:root {
  --primary: #4F46E5;
  --primary-dark: #3730A3;
  --primary-light: #818CF8;
  --accent: #06B6D4;
  --dark: #0F172A;
  --gray-900: #1E293B;
  --gray-800: #334155;
  --gray-600: #64748B;
  --gray-400: #94A3B8;
  --gray-200: #E2E8F0;
  --gray-100: #F1F5F9;
  --gray-50: #F8FAFC;
  --white: #FFFFFF;
  --bg-body: var(--gray-50);
  --bg-section: var(--white);
  --bg-card: var(--white);
  --text-primary: var(--dark);
  --text-secondary: var(--gray-600);
  --text-muted: var(--gray-400);
  --border-color: var(--gray-200);
  --gradient-1: linear-gradient(135deg, #4F46E5, #7C3AED);
  --gradient-2: linear-gradient(135deg, #059669, #10B981);
  --gradient-3: linear-gradient(135deg, #D97706, #F59E0B);
  --gradient-4: linear-gradient(135deg, #DC2626, #EF4444);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 40px rgba(0,0,0,0.12);
  --shadow-xl: 0 20px 60px rgba(0,0,0,0.15);
  --radius: 16px;
  --radius-sm: 8px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ====== 夜间模式 ====== */
[data-theme="dark"] {
  --primary: #818CF8;
  --primary-dark: #6366F1;
  --primary-light: #A5B4FC;
  --accent: #22D3EE;
  --dark: #F1F5F9;
  --gray-900: #E2E8F0;
  --gray-800: #CBD5E1;
  --gray-600: #94A3B8;
  --gray-400: #64748B;
  --gray-200: #334155;
  --gray-100: #1E293B;
  --gray-50: #0F172A;
  --white: #1E293B;
  --bg-body: #0F172A;
  --bg-section: #1E293B;
  --bg-card: #334155;
  --text-primary: #F1F5F9;
  --text-secondary: #94A3B8;
  --text-muted: #64748B;
  --border-color: #334155;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.4);
  --shadow-lg: 0 10px 40px rgba(0,0,0,0.5);
  --shadow-xl: 0 20px 60px rgba(0,0,0,0.6);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  color: var(--text-primary);
  background: var(--bg-body);
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-tap-highlight-color: transparent;
  /* 防止移动端 overscroll 导致的白色背景露出 */
  overscroll-behavior: none;
}

/* 禁止移动菜单打开时主页面滚动 */
body.menu-open { overflow: hidden; }

/* 选中颜色统一 */
::selection { background: rgba(79,70,229,0.2); color: var(--dark); }

@media (max-width: 480px) {
  body { -webkit-text-size-adjust: 100%; }
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }

/* ====== 导航栏 ====== */
.header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  background: var(--header-bg, rgba(255,255,255,0.8));
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-color);
  transition: var(--transition);
}
[data-theme="dark"] .header {
  --header-bg: rgba(15,23,42,0.85);
}
.header.scrolled { box-shadow: var(--shadow-md); }
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 72px;
}
.logo {
  display: flex; align-items: center; gap: 10px;
  font-size: 22px; font-weight: 800; color: var(--text-primary);
  text-decoration: none;
}
.logo i { font-size: 28px; color: var(--primary); }
.logo-accent { color: var(--primary); }

.nav-list {
  display: flex; gap: 8px;
  list-style: none;
}
.nav-link {
  text-decoration: none; color: var(--text-secondary); font-weight: 500;
  padding: 8px 16px; border-radius: var(--radius-sm);
  transition: var(--transition); font-size: 15px;
}
.nav-link:hover, .nav-link.active {
  color: var(--primary);
  background: rgba(79,70,229,0.08);
}
@media (max-width: 1100px) and (min-width: 769px) {
  .nav-link { padding: 8px 10px; font-size: 13px; }
  .nav-list { gap: 2px; }
}
@media (max-width: 768px) {
  .nav-link:active { background: rgba(79,70,229,0.15); }
}

/* Mobile menu */
.mobile-menu-toggle {
  display: none; flex-direction: column; gap: 5px;
  background: none; border: none; cursor: pointer; padding: 4px;
}
.mobile-menu-toggle span {
  width: 24px; height: 2px; background: var(--text-primary);
  border-radius: 2px; transition: var(--transition);
}

/* ====== 英雄区 ====== */
.hero {
  min-height: 100vh;
  display: flex; align-items: center;
  padding-top: 72px;
  position: relative; overflow: hidden;
  background: linear-gradient(135deg, #0F172A 0%, #1E293B 50%, #0F172A 100%);
}
.hero-bg { position: absolute; inset: 0; overflow: hidden; }
.orbit-circle {
  position: absolute; border-radius: 50%;
  border: 1px solid rgba(79,70,229,0.15);
  animation: orbitPulse 6s ease-in-out infinite;
}
@keyframes orbitPulse {
  0%, 100% { transform: scale(1); opacity: 0.5; }
  50% { transform: scale(1.1); opacity: 1; }
}
.hero-content {
  display: grid; grid-template-columns: 1fr 1fr;
  gap: 60px; align-items: center;
  position: relative; z-index: 1;
}
.hero-badge {
  display: inline-flex; align-items: center; gap: 8px;
  background: rgba(79,70,229,0.15);
  color: var(--primary-light);
  padding: 8px 16px; border-radius: 100px;
  font-size: 14px; font-weight: 500;
  margin-bottom: 24px; border: 1px solid rgba(79,70,229,0.2);
}
.hero h1 {
  font-size: 56px; font-weight: 800; line-height: 1.15;
  color: var(--white); margin-bottom: 20px;
}
.highlight {
  background: linear-gradient(135deg, var(--primary-light), var(--accent));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero p {
  font-size: 18px; color: var(--gray-400);
  margin-bottom: 32px; max-width: 520px;
}
.hero-actions { display: flex; gap: 16px; margin-bottom: 48px; }
.hero-stats { display: flex; gap: 40px; }
.stat-item { display: flex; flex-direction: column; }
.stat-number {
  font-size: 36px; font-weight: 800; color: var(--white);
  background: linear-gradient(135deg, var(--primary-light), var(--accent));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  background-clip: text;
}
.stat-label { font-size: 14px; color: var(--gray-400); margin-top: 4px; }

/* Globe visual */
.hero-visual { display: flex; justify-content: center; position: relative; }
.globe-card {
  width: 360px; height: 360px;
  background: radial-gradient(circle at 30% 30%, rgba(79,70,229,0.2), transparent 70%);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  position: relative;
  animation: float 6s ease-in-out infinite;
}
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-20px); }
}
.globe-icon { font-size: 120px; color: var(--primary-light); opacity: 0.8; }
.floating-tag {
  position: absolute; padding: 8px 16px;
  background: rgba(15,23,42,0.9);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(79,70,229,0.3);
  border-radius: 100px;
  color: var(--white); font-size: 14px; font-weight: 500;
  animation: floatTag 4s ease-in-out infinite;
}
.tag-1 { top: 10%; right: 0; animation-delay: 0s; }
.tag-2 { bottom: 15%; right: -10%; animation-delay: 1s; }
.tag-3 { bottom: 5%; left: 0; animation-delay: 2s; }
.tag-4 { top: 20%; left: -10%; animation-delay: 3s; }
@keyframes floatTag {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

/* ====== 通用区块 ====== */
.section { padding: 100px 0; }
.section-alt { background: var(--bg-section); }
.section-header {
  text-align: center; margin-bottom: 60px;
}
.section-tag {
  display: inline-block;
  background: rgba(79,70,229,0.1);
  color: var(--primary);
  padding: 6px 14px; border-radius: 100px;
  font-size: 12px; font-weight: 600; letter-spacing: 1px;
  margin-bottom: 16px;
}
.section-header h2 {
  font-size: 40px; font-weight: 800; color: var(--text-primary);
  margin-bottom: 12px;
}
.section-header p {
  font-size: 18px; color: var(--gray-600);
  max-width: 500px; margin: 0 auto;
}

/* ====== 按钮 ====== */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 14px 28px; border-radius: var(--radius-sm);
  font-size: 15px; font-weight: 600;
  text-decoration: none; cursor: pointer;
  border: none; transition: var(--transition);
}
.btn-primary {
  background: var(--gradient-1);
  color: var(--white);
  box-shadow: 0 4px 15px rgba(79,70,229,0.3);
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(79,70,229,0.4);
}
.btn-outline {
  background: transparent;
  color: var(--white);
  border: 2px solid rgba(255,255,255,0.2);
}
.btn-outline:hover {
  border-color: var(--primary-light);
  background: rgba(79,70,229,0.1);
}

/* ====== 资源卡片 ====== */
.resource-grid {
  display: grid; grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}
.resource-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 32px;
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: transform 0.35s cubic-bezier(0.4,0,0.2,1), box-shadow 0.35s ease, border-color 0.35s ease;
  position: relative;
  overflow: hidden;
}
.resource-card::before {
  content: '';
  position: absolute; top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--gradient-1);
  opacity: 0;
  transition: opacity 0.35s ease;
}
.resource-card:nth-child(2)::before { background: var(--gradient-2); }
.resource-card:nth-child(3)::before { background: var(--gradient-3); }
.resource-card:nth-child(4)::before { background: var(--gradient-4); }
.resource-card:hover::before { opacity: 1; }
.resource-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-xl);
  border-color: transparent;
}
.resource-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-lg);
  border-color: transparent;
}
.card-diff {
  position: absolute; top: 16px; right: 16px;
  font-size: 12px; font-weight: 600;
  padding: 4px 10px; border-radius: 100px;
}
.diff-beginner {
  background: rgba(16,185,129,0.12);
  color: #059669;
  border: 1px solid rgba(16,185,129,0.2);
}
.diff-intermediate {
  background: rgba(245,158,11,0.12);
  color: #D97706;
  border: 1px solid rgba(245,158,11,0.2);
}
.diff-advanced {
  background: rgba(239,68,68,0.12);
  color: #DC2626;
  border: 1px solid rgba(239,68,68,0.2);
}

/* ====== 难度导航 ====== */
.difficulty-nav {
  display: flex; justify-content: center; gap: 12px;
  margin-bottom: 32px; flex-wrap: wrap;
}
.diff-tag {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 8px 18px; border-radius: 100px;
  font-size: 14px; font-weight: 600;
  cursor: default;
  transition: var(--transition);
}
.diff-tag.diff-beginner {
  background: rgba(16,185,129,0.1);
  color: #059669;
  border: 1px solid rgba(16,185,129,0.2);
}
.diff-tag.diff-intermediate {
  background: rgba(245,158,11,0.1);
  color: #D97706;
  border: 1px solid rgba(245,158,11,0.2);
}
.diff-tag.diff-advanced {
  background: rgba(239,68,68,0.1);
  color: #DC2626;
  border: 1px solid rgba(239,68,68,0.2);
}
.card-icon {
  width: 56px; height: 56px;
  border-radius: 14px;
  display: flex; align-items: center; justify-content: center;
  margin-bottom: 20px;
}
.card-icon i { font-size: 24px; color: var(--white); }
.resource-card h3 {
  font-size: 18px; font-weight: 700; margin-bottom: 10px;
  color: var(--text-primary);
}
.resource-card p {
  font-size: 14px; color: var(--gray-600);
  line-height: 1.6; margin-bottom: 20px;
}
.card-meta {
  display: flex; gap: 16px;
  font-size: 13px; color: var(--gray-400);
}
.card-meta i { margin-right: 4px; }

/* ====== 竞赛信息 ====== */
.competition-content {
  display: grid; grid-template-columns: 1fr 1fr;
  gap: 60px; align-items: start;
}
.comp-timeline { position: relative; padding-left: 30px; }
.comp-timeline::before {
  content: ''; position: absolute; left: 8px; top: 0; bottom: 0;
  width: 2px; background: var(--gray-200);
}
.timeline-item { position: relative; margin-bottom: 40px; }
.timeline-dot {
  position: absolute; left: -26px; top: 4px;
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--primary); border: 3px solid var(--gray-100);
}
.timeline-date {
  font-size: 13px; font-weight: 600; color: var(--primary);
  text-transform: uppercase; letter-spacing: 1px;
}
.timeline-content h4 {
  font-size: 18px; font-weight: 700; margin: 4px 0 8px;
}
.timeline-content p { color: var(--gray-600); font-size: 14px; }

.comp-info-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 20px;
}
.info-card {
  background: var(--gray-50);
  padding: 24px; border-radius: var(--radius);
  border: 1px solid var(--border-color);
  transition: transform 0.35s cubic-bezier(0.4,0,0.2,1), box-shadow 0.35s ease, border-color 0.35s ease;
  position: relative; overflow: hidden;
}
.info-card::after {
  content: ''; position: absolute; top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--gradient-1);
  opacity: 0; transition: opacity 0.35s ease;
}
.info-card:nth-child(2)::after { background: var(--gradient-2); }
.info-card:nth-child(3)::after { background: var(--gradient-3); }
.info-card:nth-child(4)::after { background: var(--gradient-4); }
.info-card:hover::after { opacity: 1; }
.info-card:hover {
  transform: translateY(-4px);
  border-color: transparent;
  box-shadow: var(--shadow-md);
}
.info-card:hover {
  border-color: var(--primary-light);
  box-shadow: var(--shadow-sm);
}
.info-card i {
  font-size: 28px; color: var(--primary); margin-bottom: 12px;
}
.info-card h4 { font-size: 16px; font-weight: 700; margin-bottom: 8px; }
.info-card p { font-size: 14px; color: var(--gray-600); margin-bottom: 12px; line-height: 1.5; }
.info-link {
  font-size: 14px; font-weight: 600; color: var(--primary);
  text-decoration: none; display: inline-flex; align-items: center; gap: 4px;
}
.info-link i { font-size: 12px; margin: 0; }

/* ====== 社区 ====== */
.community-grid {
  display: grid; grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.community-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 28px;
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: transform 0.35s cubic-bezier(0.4,0,0.2,1), box-shadow 0.35s ease, border-color 0.35s ease;
  position: relative;
  overflow: hidden;
}
.community-card::before {
  content: '';
  position: absolute; top: 0; left: 20px; right: 20px;
  height: 3px;
  background: var(--gradient-1);
  border-radius: 0 0 3px 3px;
  opacity: 0;
  transition: opacity 0.35s ease;
}
.community-card:nth-child(2)::before { background: var(--gradient-2); }
.community-card:nth-child(3)::before { background: var(--gradient-3); }
.community-card:hover::before { opacity: 1; }
.community-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: transparent;
}
.community-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: transparent;
}
.community-card-header {
  display: flex; align-items: center; gap: 12px;
  margin-bottom: 16px;
}
.avatar {
  width: 44px; height: 44px; border-radius: 50%;
}
.community-card-header h4 {
  font-size: 15px; font-weight: 700;
}
.post-time {
  font-size: 12px; color: var(--gray-400);
}
.community-card > h4 {
  font-size: 16px; font-weight: 600;
  margin-bottom: 8px; line-height: 1.4;
  color: var(--text-primary);
}
.community-card > p {
  font-size: 14px; color: var(--gray-600);
  line-height: 1.6; margin-bottom: 16px;
}
.post-actions {
  display: flex; gap: 20px;
  font-size: 13px; color: var(--gray-400);
}
.post-actions i { margin-right: 4px; }
.post-actions span { cursor: pointer; transition: var(--transition); }
.post-actions span:hover { color: var(--primary); }

.community-cta {
  text-align: center; margin-top: 48px;
}

/* ====== 推荐教材 ====== */
.textbook-list {
  max-width: 800px; margin: 0 auto;
  display: flex; flex-direction: column; gap: 16px;
}
.textbook-item {
  display: flex; gap: 20px; align-items: flex-start;
  background: var(--bg-card);
  padding: 24px;
  border-radius: var(--radius);
  border: 1px solid var(--border-color);
  transition: var(--transition);
}
.textbook-item:hover {
  transform: translateX(4px);
  border-color: var(--primary-light);
  box-shadow: var(--shadow-sm);
}
.textbook-rank {
  font-size: 32px; line-height: 1;
  min-width: 48px; text-align: center;
}
.textbook-info h4 {
  font-size: 17px; font-weight: 700;
  margin-bottom: 4px;
}
.textbook-author {
  font-size: 14px; color: var(--primary);
  font-weight: 500; margin-bottom: 6px;
}
.textbook-desc {
  font-size: 14px; color: var(--gray-600);
  line-height: 1.6;
}

/* ====== 搜索 ====== */
.search-wrapper {
  max-width: 700px; margin: 0 auto;
}
.search-box {
  display: flex; align-items: center; gap: 0;
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 4px;
  border: 2px solid var(--gray-200);
  transition: var(--transition);
}
.search-box:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(79,70,229,0.1);
}
.search-icon {
  padding: 0 16px; color: var(--gray-400);
  font-size: 18px;
}
.search-box input {
  flex: 1; border: none; outline: none;
  font-size: 16px; font-family: inherit;
  padding: 12px 0;
  background: transparent;
}
.search-box .btn {
  border-radius: var(--radius-sm);
  padding: 12px 28px;
}
.search-results {
  margin-top: 20px;
}
.search-result-item {
  background: var(--bg-card);
  padding: 16px 20px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  margin-bottom: 8px;
  animation: slideIn 0.3s ease;
}
.search-result-item h4 { font-size: 15px; font-weight: 600; }
.search-result-item p { font-size: 13px; color: var(--gray-600); margin-top: 4px; }
@keyframes slideIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ====== 模态框 ====== */
.modal-overlay {
  display: none; position: fixed; inset: 0;
  background: rgba(0,0,0,0.5);
  backdrop-filter: blur(4px);
  z-index: 2000;
  align-items: center; justify-content: center;
  animation: fadeIn 0.2s ease;
}
.modal-overlay.show { display: flex; }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
.modal {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 40px;
  max-width: 520px; width: 90%;
  max-height: 80vh; overflow-y: auto;
  position: relative;
  animation: scaleIn 0.3s ease;
}
@keyframes scaleIn {
  from { transform: scale(0.9); opacity: 0; }
  to { transform: scale(1); opacity: 1; }
}
.modal-close {
  position: absolute; top: 16px; right: 16px;
  background: var(--gray-100); border: none;
  width: 36px; height: 36px; border-radius: 50%;
  cursor: pointer; font-size: 16px;
  display: flex; align-items: center; justify-content: center;
  transition: var(--transition);
}
.modal-close:hover { background: var(--gray-200); }

/* Modal form styling */
.form-group { margin-bottom: 20px; }
.form-group label {
  display: block; font-size: 14px; font-weight: 600;
  margin-bottom: 6px; color: var(--gray-800);
}
.form-group input,
.form-group textarea,
.form-group select {
  width: 100%; padding: 12px 16px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  font-size: 15px; font-family: inherit;
  transition: var(--transition); outline: none;
}
.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79,70,229,0.1);
}
.form-group textarea { min-height: 100px; resize: vertical; }
.form-row { display: flex; gap: 16px; }
.form-row .form-group { flex: 1; }

.btn-mock-exam {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 18px 40px; border-radius: var(--radius-sm);
  font-size: 17px; font-weight: 700;
  text-decoration: none; cursor: pointer;
  border: none; transition: var(--transition);
  background: linear-gradient(135deg, #DC2626, #EF4444);
  color: var(--white);
  box-shadow: 0 4px 20px rgba(220,38,38,0.35);
  font-family: inherit;
}
.btn-mock-exam:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(220,38,38,0.45);
}

/* 模拟考试计时警告 */
.timer-warning { color: #DC2626 !important; animation: timerPulse 1s ease-in-out infinite; }
@keyframes timerPulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

/* ====== 社区帖子系统 ====== */
.community-tabs {
  display: flex; gap: 8px; justify-content: center; margin-bottom: 32px;
}
.community-tab {
  padding: 8px 20px; border-radius: 100px;
  border: 1px solid var(--border-color); background: var(--white);
  cursor: pointer; font-size: 14px; font-weight: 500; color: var(--gray-600);
  transition: var(--transition); font-family: inherit;
}
.community-tab:hover { border-color: var(--primary-light); color: var(--primary); }
.community-tab.active { background: var(--primary); color: var(--white); border-color: var(--primary); }

.community-toolbar {
  display: flex; justify-content: space-between; align-items: center;
  margin-bottom: 24px; flex-wrap: wrap; gap: 12px;
}
.community-search {
  display: flex; align-items: center; gap: 8px;
  padding: 8px 16px; background: var(--white);
  border: 1px solid var(--border-color); border-radius: var(--radius-sm);
  flex: 1; max-width: 300px;
}
.community-search input {
  border: none; outline: none; font-size: 14px;
  font-family: inherit; flex: 1; background: transparent;
}

.post-modal-header { margin-bottom: 16px; }
.post-modal-header .form-group textarea { min-height: 120px; }
.post-tags {
  display: flex; gap: 6px; flex-wrap: wrap; margin: 12px 0;
}
.post-tag {
  display: inline-block; padding: 4px 12px;
  border-radius: 100px; font-size: 12px; font-weight: 500;
  cursor: pointer; transition: var(--transition);
  border: 1px solid transparent;
}
.post-tag:hover { opacity: 0.8; }
.tag-geology { background: rgba(79,70,229,0.1); color: #4F46E5; border-color: rgba(79,70,229,0.2); }
.tag-meteorology { background: rgba(5,150,105,0.1); color: #059669; border-color: rgba(5,150,105,0.2); }
.tag-oceanography { background: rgba(6,182,212,0.1); color: #06B6D4; border-color: rgba(6,182,212,0.2); }
.tag-astronomy { background: rgba(217,119,6,0.1); color: #D97706; border-color: rgba(217,119,6,0.2); }
.tag-general { background: rgba(99,102,241,0.1); color: #6366F1; border-color: rgba(99,102,241,0.2); }

.post-like-btn.liked { color: #DC2626 !important; }
.post-like-btn.liked i { font-weight: 900; }

.post-bookmark-btn { color: var(--gray-400); }
.post-bookmark-btn:hover { color: var(--primary) !important; }
.post-bookmark-btn.bookmarked { color: var(--primary) !important; }
.post-bookmark-btn.bookmarked i { font-weight: 900; }

.comment-item {
  padding: 16px; background: var(--gray-50);
  border-radius: var(--radius-sm); margin-bottom: 12px;
}
.comment-header {
  display: flex; align-items: center; gap: 10px; margin-bottom: 8px;
}
.comment-avatar {
  width: 32px; height: 32px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 14px; font-weight: 600;
}
.comment-author { font-size: 14px; font-weight: 600; }
.comment-time { font-size: 12px; color: var(--gray-400); }
.comment-text { font-size: 14px; color: var(--gray-600); line-height: 1.6; }
.quiz-container {
  max-width: 720px; margin: 0 auto;
}
.quiz-category-grid {
  display: grid; grid-template-columns: repeat(3, 1fr);
  gap: 16px; margin-bottom: 32px;
}
.quiz-cat-btn {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 24px;
  cursor: pointer;
  text-align: center;
  transition: var(--transition);
  font-family: inherit;
}
.quiz-cat-btn:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: transparent;
}
.quiz-cat-all { grid-column: 2; }
.qcat-icon {
  display: inline-flex; align-items: center; justify-content: center;
  width: 56px; height: 56px; border-radius: 14px;
  font-size: 24px; margin-bottom: 12px;
}
.qcat-name {
  display: block; font-size: 16px; font-weight: 700;
  color: var(--text-primary); margin-bottom: 4px;
}
.qcat-count {
  font-size: 13px; color: var(--gray-400);
}
.quiz-stats-bar {
  display: flex; align-items: center; justify-content: center;
  gap: 24px; padding: 16px 24px;
  background: var(--bg-card); border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  font-size: 14px; color: var(--gray-600);
  flex-wrap: wrap;
}
.qs-item { display: flex; align-items: center; gap: 6px; }
.qs-item strong { color: var(--text-primary); }

/* 答题面板 */
.quiz-header { margin-bottom: 24px; }
.quiz-progress-bar {
  height: 4px; background: var(--gray-200);
  border-radius: 2px; margin-bottom: 12px; overflow: hidden;
}
.quiz-progress-fill {
  height: 100%; background: var(--gradient-1);
  border-radius: 2px; transition: width 0.5s ease; width: 0%;
}
.quiz-header-info {
  display: flex; justify-content: space-between;
  font-size: 14px; color: var(--gray-400);
}
.quiz-question {
  font-size: 20px; font-weight: 700;
  line-height: 1.5; margin-bottom: 24px;
  color: var(--text-primary);
}
.quiz-options { display: grid; gap: 12px; margin-bottom: 24px; }
.quiz-option {
  display: flex; align-items: center; gap: 14px;
  padding: 16px 20px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  font-size: 16px; font-family: inherit;
  background: var(--bg-card); text-align: left;
}
.quiz-option:hover { border-color: var(--primary-light); background: rgba(79,70,229,0.03); }
.quiz-option.selected { border-color: var(--primary); background: rgba(79,70,229,0.06); }
.quiz-option.correct {
  border-color: #059669; background: rgba(16,185,129,0.08);
}
.quiz-option.wrong {
  border-color: #DC2626; background: rgba(239,68,68,0.08);
}
.quiz-option .qopt-label {
  width: 28px; height: 28px;
  border-radius: 50%; background: var(--gray-100);
  display: flex; align-items: center; justify-content: center;
  font-size: 14px; font-weight: 600; color: var(--gray-600);
  flex-shrink: 0;
}
.quiz-option.selected .qopt-label { background: var(--primary); color: var(--white); }
.quiz-option.correct .qopt-label { background: #059669; color: var(--white); }
.quiz-option.wrong .qopt-label { background: #DC2626; color: var(--white); }
.quiz-option.disabled { pointer-events: none; }

.quiz-explanation {
  padding: 20px; background: rgba(79,70,229,0.06);
  border-radius: var(--radius-sm);
  border-left: 4px solid var(--primary);
  margin-bottom: 24px;
  animation: slideIn 0.3s ease;
}
.quiz-explanation h5 {
  font-size: 15px; font-weight: 700; margin-bottom: 8px;
  color: var(--primary);
}
.quiz-explanation p {
  font-size: 14px; color: var(--gray-600); line-height: 1.7;
}
.quiz-actions {
  display: flex; justify-content: space-between; gap: 16px;
}

/* 结果面板 */
.qr-header { text-align: center; margin-bottom: 32px; }
.qr-big-icon { font-size: 56px; margin-bottom: 12px; }
.qr-header h3 { font-size: 24px; font-weight: 700; }
.qr-stats {
  display: grid; grid-template-columns: repeat(4, 1fr);
  gap: 16px; margin-bottom: 24px;
}
.qr-stat {
  text-align: center; padding: 20px;
  background: var(--gray-50); border-radius: var(--radius-sm);
}
.qr-stat span:first-child {
  display: block; font-size: 32px; font-weight: 800;
  color: var(--text-primary);
}
.qs-label { font-size: 13px; color: var(--gray-400); }
.qr-score-bar {
  height: 8px; background: var(--gray-200);
  border-radius: 4px; margin-bottom: 24px; overflow: hidden;
}
.qr-score-fill { height: 100%; border-radius: 4px; transition: width 1s ease; }
.qr-actions {
  display: flex; justify-content: center; gap: 16px;
}

/* ====== 页脚 ====== */
.footer {
  background: var(--dark); color: var(--gray-400);
  padding: 80px 0 0;
}
.footer-grid {
  display: grid; grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px; padding-bottom: 40px;
  border-bottom: 1px solid var(--gray-800);
}
.footer-brand i { font-size: 32px; color: var(--primary-light); margin-bottom: 16px; }
.footer-brand h3 {
  font-size: 20px; font-weight: 700; color: var(--white);
  margin-bottom: 12px;
}
.footer-brand p { font-size: 14px; line-height: 1.7; }
.social-links { display: flex; gap: 12px; margin-top: 20px; }
.social-links a {
  width: 40px; height: 40px; border-radius: 50%;
  background: var(--gray-800); color: var(--gray-400);
  display: flex; align-items: center; justify-content: center;
  text-decoration: none; font-size: 18px;
  transition: var(--transition);
}
.social-links a:hover {
  background: var(--primary); color: var(--white);
}
.footer-links h4 {
  color: var(--white); font-size: 16px; font-weight: 600;
  margin-bottom: 20px;
}
.footer-links a {
  display: block; color: var(--gray-400);
  text-decoration: none; font-size: 14px;
  margin-bottom: 12px; transition: var(--transition);
}
.footer-links a:hover { color: var(--primary-light); }
.footer-bottom {
  text-align: center; padding: 24px 0;
  font-size: 14px;
}

/* ====== 面包屑导航 ====== */
.breadcrumb {
  position: fixed; top: 72px; left: 0; right: 0; z-index: 999;
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  padding: 10px 0;
  font-size: 13px;
}
.breadcrumb a {
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition);
}
.breadcrumb a:hover { opacity: 0.7; }
.bc-sep { margin: 0 8px; color: var(--gray-400); }
.bc-current { color: var(--gray-600); font-weight: 500; }

/* ====== 资源浏览器 ====== */
.res-filter-bar {
  display: flex; gap: 12px; flex-wrap: wrap;
  margin-bottom: 24px; align-items: center;
}
.res-filter-bar select {
  padding: 10px 16px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  font-size: 14px; font-family: inherit;
  background: var(--bg-card);
  color: var(--gray-800);
  cursor: pointer;
  transition: var(--transition);
  outline: none;
  min-width: 130px;
}
.res-filter-bar select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79,70,229,0.1);
}
.res-filter-search {
  display: flex; align-items: center; gap: 8px;
  padding: 0 16px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  flex: 1; min-width: 200px;
  transition: var(--transition);
}
.res-filter-search:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79,70,229,0.1);
}
.res-filter-search i { color: var(--gray-400); font-size: 14px; }
.res-filter-search input {
  border: none; outline: none; padding: 10px 0;
  font-size: 14px; font-family: inherit;
  flex: 1; background: transparent;
}
.res-browser-list {
  display: flex; flex-direction: column; gap: 8px;
}
.res-browser-item {
  background: var(--bg-card);
  padding: 16px 20px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  transition: var(--transition);
}
.res-browser-item:hover {
  border-color: var(--primary-light);
  box-shadow: var(--shadow-sm);
}
.rbi-top {
  display: flex; justify-content: space-between;
  align-items: center; margin-bottom: 6px;
}
.rbi-top h4 { font-size: 15px; font-weight: 600; color: var(--text-primary); }
.diff-badge {
  font-size: 11px; font-weight: 600;
  padding: 3px 10px; border-radius: 100px;
  white-space: nowrap;
}
.diff-badge.tag-beginner { background: rgba(16,185,129,0.12); color: #059669; border: 1px solid rgba(16,185,129,0.2); }
.diff-badge.tag-intermediate { background: rgba(245,158,11,0.12); color: #D97706; border: 1px solid rgba(245,158,11,0.2); }
.diff-badge.tag-advanced { background: rgba(239,68,68,0.12); color: #DC2626; border: 1px solid rgba(239,68,68,0.2); }
.rbi-meta {
  display: flex; gap: 12px; align-items: center;
  font-size: 13px; color: var(--gray-400);
}
.rbi-type { font-weight: 600; color: var(--primary); }
.rbi-cat { color: var(--gray-600); }
.rbi-link {
  margin-left: auto;
  color: var(--primary); text-decoration: none;
  font-weight: 500;
}
.rbi-link:hover { text-decoration: underline; }

/* ====== 标签云 ====== */
.tag-cloud {
  display: flex; flex-wrap: wrap; gap: 12px;
  justify-content: center; padding: 20px 0;
}
.cloud-tag {
  display: inline-block;
  padding: 6px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 100px;
  color: var(--primary);
  cursor: pointer;
  transition: var(--transition);
  font-weight: 500;
}
.cloud-tag:hover {
  background: var(--primary);
  color: var(--white);
  border-color: var(--primary);
  transform: scale(1.05);
}

/* ====== 阅读进度条 ====== */
.reading-progress {
  position: fixed; top: 72px; left: 0; right: 0; z-index: 1001;
  height: 3px;
  background: transparent;
  pointer-events: none;
}
.rp-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  transition: width 0.1s linear;
}

/* ====== 夜间模式切换按钮 ====== */
.theme-toggle-btn {
  font-size: 16px !important;
}

/* ====== 自定义滚动条（PC） ====== */
@media (hover: hover) {
  ::-webkit-scrollbar { width: 8px; }
  ::-webkit-scrollbar-track { background: var(--gray-100); }
  ::-webkit-scrollbar-thumb {
    background: var(--gray-300, var(--gray-400));
    border-radius: 4px;
  }
  ::-webkit-scrollbar-thumb:hover { background: var(--gray-400, var(--gray-600)); }
}

/* ====== 骨架屏加载动画 ====== */
@keyframes skeletonShimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}
.skeleton {
  background: linear-gradient(90deg, var(--bg-card) 25%, var(--gray-200) 50%, var(--bg-card) 75%);
  background-size: 200% 100%;
  animation: skeletonShimmer 1.5s ease-in-out infinite;
  border-radius: var(--radius-sm);
}
.skeleton-card {
  height: 200px; border-radius: var(--radius);
}
.skeleton-text { height: 16px; margin-bottom: 10px; width: 80%; }
.skeleton-text-short { height: 16px; width: 40%; }
.skeleton-avatar {
  width: 44px; height: 44px; border-radius: 50%;
}

/* ====== 键盘快捷键提示 ====== */
.kbd-hint {
  position: fixed; bottom: 24px; right: 24px; z-index: 999;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 14px 18px;
  box-shadow: var(--shadow-lg);
  font-size: 13px;
  opacity: 0;
  transform: translateY(20px);
  transition: var(--transition);
  pointer-events: none;
  max-width: 220px;
}
.kbd-hint.show {
  opacity: 1;
  transform: translateY(0);
}
.kbd-hint kbd {
  display: inline-block;
  padding: 2px 8px;
  background: var(--gray-100);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-size: 12px;
  font-family: inherit;
  margin: 0 2px;
}
.kbd-hint-row {
  display: flex; align-items: center; gap: 10px;
  padding: 4px 0;
  color: var(--text-secondary);
}

/* ====== 夜间模式微调 ====== */
[data-theme="dark"] .hero p { color: var(--gray-400); }
[data-theme="dark"] .stat-label { color: var(--gray-400); }
[data-theme="dark"] .floating-tag { background: rgba(30,41,59,0.9); }
[data-theme="dark"] .timeline-item { border-left-color: var(--border-color) !important; }
[data-theme="dark"] .quiz-stats-bar .btn-outline { color: var(--text-secondary) !important; border-color: var(--border-color) !important; }
[data-theme="dark"] .quiz-actions .btn-outline { color: var(--text-secondary) !important; border-color: var(--border-color) !important; }
[data-theme="dark"] .qr-actions .btn-outline { color: var(--text-secondary) !important; border-color: var(--border-color) !important; }
[data-theme="dark"] .community-search input { color: var(--text-primary); }

/* ====== 动画 ====== */
.fade-in {
  opacity: 0; transform: translateY(30px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}
.fade-in.visible {
  opacity: 1; transform: translateY(0);
}

/* ====== 错题本 ====== */
.wrong-review-bar {
  text-align: center;
  margin-top: 16px;
}
.wrong-review-bar .btn {
  transition: all 0.3s ease;
}
.wrong-review-bar .btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

/* ====== 学习路线图 ====== */
.roadmap-container {
  max-width: 800px;
  margin: 0 auto;
  position: relative;
  padding: 20px 0;
}

.roadmap-phase {
  display: flex;
  align-items: flex-start;
  gap: 24px;
  padding: 24px;
  background: var(--bg-card);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  transition: all 0.3s ease;
}
.roadmap-phase:hover {
  transform: translateX(4px);
  box-shadow: var(--shadow-md);
  border-color: var(--primary-light);
}

.phase-number {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--gradient-1);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  font-weight: 700;
  flex-shrink: 0;
}

.phase-content { flex: 1; }

.phase-badge {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 8px;
}
.phase-beginner { background: rgba(16,185,129,0.12); color: #059669; }
.phase-intermediate { background: rgba(245,158,11,0.12); color: #D97706; }
.phase-advanced { background: rgba(239,68,68,0.12); color: #DC2626; }

.phase-content h4 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--text-primary);
}

.phase-content ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.phase-content ul li {
  position: relative;
  padding-left: 20px;
  margin-bottom: 6px;
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}
.phase-content ul li::before {
  content: '→';
  position: absolute;
  left: 0;
  color: var(--primary);
  font-weight: 600;
}

.roadmap-connector {
  width: 2px;
  height: 32px;
  background: linear-gradient(180deg, var(--primary-light), var(--primary));
  margin: 0 auto;
  opacity: 0.4;
}

/* ============================================
   响应式设计 — 四断点适配 (1024 / 768 / 640 / 480)
   ============================================ */

/* ---- Large: 1024px ↓ ---- */
@media (max-width: 1024px) {
  .hero h1 { font-size: 44px; }
  .resource-grid { grid-template-columns: repeat(2, 1fr); }
  .competition-content { grid-template-columns: 1fr; gap: 40px; }
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 32px; }
  .community-grid { grid-template-columns: repeat(2, 1fr); }
  .globe-card { width: 280px; height: 280px; }
  .globe-icon { font-size: 90px; }
  .tag-2 { right: 0; }
  .tag-4 { left: 0; }
  .textbook-list { max-width: 100%; }
}

/* ---- Medium: 768px ↓ ---- */
@media (max-width: 768px) {
  /* ========== 汉堡菜单 ========== */
  .mobile-menu-toggle { display: flex; }

  .nav {
    position: fixed; top: 72px; left: 0; right: 0;
    background: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    padding: 12px 20px 20px;
    transform: translateY(-110%); opacity: 0;
    transition: transform 0.35s cubic-bezier(0.4,0,0.2,1), opacity 0.25s ease;
    pointer-events: none;
    z-index: 999;
    max-height: calc(100vh - 80px);
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
  }
  .nav.open {
    transform: translateY(0); opacity: 1;
    pointer-events: auto;
  }
  .nav-list {
    flex-direction: column; gap: 2px;
  }
  .nav-link {
    display: flex; align-items: center;
    padding: 14px 16px; font-size: 16px;
    border-radius: var(--radius-sm);
    min-height: 48px; /* 触控友好 */
  }

  /* 移动菜单打开时禁止背景滚动 */
  body.menu-open { overflow: hidden; }

  /* ========== Hero ========== */
  .hero-content {
    grid-template-columns: 1fr; text-align: center;
  }
  .hero { min-height: auto; padding: 100px 0 60px; }
  .hero h1 { font-size: 36px; }
  .hero p { margin: 0 auto 32px; max-width: 100%; }
  .hero-actions { justify-content: center; flex-wrap: wrap; }
  .hero-stats { justify-content: center; gap: 32px; }
  .hero-visual { display: none; }
  .stat-number { font-size: 28px; }

  /* ========== 区块 ========== */
  .section { padding: 64px 0; }
  .section-header { margin-bottom: 40px; }
  .section-header h2 { font-size: 32px; }
  .section-header p { font-size: 16px; }

  /* ========== 资源卡片 ========== */
  .resource-grid { grid-template-columns: 1fr; gap: 16px; }
  .resource-card { padding: 24px; }
  .resource-card h3 { font-size: 17px; }
  .card-icon { width: 48px; height: 48px; }
  .card-icon i { font-size: 20px; }

  /* ========== 难度导航 ========== */
  .difficulty-nav { gap: 8px; }

  /* ========== 资源浏览器 ========== */
  .res-filter-bar {
    flex-direction: column; gap: 8px;
  }
  .res-filter-bar select {
    width: 100%; min-width: unset;
  }
  .res-filter-search { width: 100%; min-width: unset; }
  .rbi-top { flex-direction: column; align-items: flex-start; gap: 6px; }
  .rbi-meta { flex-wrap: wrap; gap: 8px; }
  .rbi-link { margin-left: 0; }

  /* ========== 竞赛信息 ========== */
  .comp-info-grid { grid-template-columns: 1fr; gap: 16px; }
  .timeline-item { margin-bottom: 28px; }

  /* ========== 社区 ========== */
  .community-grid { grid-template-columns: 1fr; gap: 16px; }
  .community-card { padding: 20px; }
  .community-toolbar { flex-direction: column; align-items: stretch; }
  .community-search { max-width: 100%; }

  /* ========== 题库 ========== */
  .quiz-category-grid {
    grid-template-columns: 1fr 1fr; gap: 12px;
  }
  .quiz-cat-btn { padding: 18px 12px; }
  .quiz-cat-all { grid-column: 1 / -1; }
  .qcat-icon { width: 48px; height: 48px; font-size: 20px; }
  .quiz-question { font-size: 17px; }
  .quiz-option { padding: 14px 16px; font-size: 15px; }
  .quiz-stats-bar {
    flex-direction: column; gap: 8px; padding: 14px 18px;
  }

  /* ========== 答题结果 ========== */
  .qr-stats { grid-template-columns: repeat(2, 1fr); gap: 12px; }
  .qr-stat { padding: 16px; }
  .qr-stat span:first-child { font-size: 26px; }
  .qr-header h3 { font-size: 20px; }

  /* ========== 推荐教材 ========== */
  .textbook-item {
    flex-direction: column; gap: 12px; padding: 20px;
  }
  .textbook-rank { font-size: 28px; min-width: unset; text-align: left; }

  /* ========== 搜索 ========== */
  .search-box { flex-wrap: wrap; padding: 8px; gap: 8px; }
  .search-box input { width: 100%; padding: 8px 12px; }
  .search-box .btn { width: 100%; justify-content: center; }
  .search-icon { display: none; }

  /* ========== 页脚 ========== */
  .footer-grid {
    grid-template-columns: 1fr 1fr; gap: 24px;
  }
  .footer { padding: 48px 0 0; }

  /* ========== 表单 ========== */
  .form-row { flex-direction: column; gap: 0; }

  /* ========== 标签云 ========== */
  .tag-cloud { gap: 8px; }
  .cloud-tag { padding: 5px 12px; font-size: 0.9rem !important; }

  /* ========== 模态框 ========== */
  .modal {
    padding: 28px 24px; max-width: 96%; width: 96%;
    max-height: 90vh;
  }

  /* ========== 模拟考试按钮 ========== */
  .btn-mock-exam { padding: 14px 28px; font-size: 15px; width: 100%; justify-content: center; }

  /* ========== 面包屑 ========== */
  .breadcrumb { font-size: 12px; padding: 8px 0; }

  /* ========== 快捷键提示 ========== */
  .kbd-hint { bottom: 16px; right: 16px; max-width: 200px; }
}

/* ---- Small: 640px ↓ ---- */
@media (max-width: 640px) {
  .container { padding: 0 16px; }
  .hero h1 { font-size: 30px; }
  .section-header h2 { font-size: 26px; }
  .section { padding: 48px 0; }
  .hero-actions .btn { flex: 1; justify-content: center; }
  .quiz-category-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: 32px; text-align: center; }
  .footer-links { text-align: center; }
  .social-links { justify-content: center; }
  .modal { padding: 24px 18px; }
  .community-tabs { gap: 6px; }
  .community-tab { padding: 6px 14px; font-size: 13px; }
  .comp-info-grid { gap: 12px; }
  .info-card { padding: 18px; }
  .btn { padding: 12px 22px; font-size: 14px; }
  .qr-stats { grid-template-columns: repeat(2, 1fr); gap: 8px; }
  .quiz-actions { flex-direction: column; }
  .quiz-actions .btn { justify-content: center; }
  .res-filter-bar select { font-size: 15px; padding: 12px 14px; }
  .res-filter-search input { font-size: 15px; }
  .res-browser-item { padding: 14px 16px; }
  .community-card > h4 { font-size: 15px; }
  .post-actions { gap: 14px; }
}

/* ---- Extra Small: 480px ↓ ---- */
@media (max-width: 480px) {
  .hero h1 { font-size: 26px; }
  .hero-badge { font-size: 12px; padding: 6px 12px; }
  .stat-number { font-size: 24px; }
  .hero-stats { gap: 20px; }
  .resource-card { padding: 18px; }
  .card-diff { font-size: 11px; padding: 3px 8px; }
  .section-header p { font-size: 14px; }
  .modal { padding: 20px 14px; border-radius: 12px; }
  .modal-close { width: 32px; height: 32px; top: 10px; right: 10px; }
  .quiz-question { font-size: 16px; }
  .quiz-option { padding: 12px 14px; font-size: 14px; }
  .quiz-option .qopt-label { width: 24px; height: 24px; font-size: 12px; }
  .nav-link { padding: 12px 14px; font-size: 15px; min-height: 44px; }
  .community-card { padding: 16px; }
  .post-tags { gap: 4px; }
  .post-tag { font-size: 11px; padding: 3px 10px; }
  .textbook-item { padding: 16px; }
  .textbook-info h4 { font-size: 15px; }
  .textbook-desc { font-size: 13px; }
  .footer { padding: 36px 0 0; }
  .footer-bottom { font-size: 12px; padding: 18px 0; }
  .breadcrumb { font-size: 11px; }
}

/* ---- 触控设备优化 ---- */
@media (hover: none) and (pointer: coarse) {
  .resource-card:hover,
  .community-card:hover,
  .textbook-item:hover,
  .quiz-cat-btn:hover,
  .info-card:hover {
    transform: none !important;
  }
  .btn-primary:hover,
  .btn-mock-exam:hover {
    transform: none !important;
  }
  .res-browser-item:hover { transform: none !important; }
  /* 触控下保持阴影指示状态，去掉位移 */
  .resource-card:active,
  .community-card:active { transform: scale(0.98); }
  .btn:active { transform: scale(0.96); }
}

/* ---- 打印样式 ---- */
@media print {
  .header, .footer, .reading-progress, .breadcrumb,
  .kbd-hint, .modal-overlay, .btn, .community-toolbar,
  .quiz-actions { display: none !important; }
  .section { padding: 20px 0; page-break-inside: avoid; }
  body { background: white; color: black; }
  .hero { background: white !important; min-height: auto; padding: 40px 0; }
  .hero h1 { color: black !important; }
  .hero p { color: #333 !important; }
}

/* ========================================
   🍎 苹果风格样式 - Apple-Style Design
   ======================================== */

/* ====== 英雄区 - 大图背景 ====== */
.hero-apple {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  padding-top: 72px;
}

.hero-bg-image {
  position: absolute;
  inset: 0;
  background: url('https://images.unsplash.com/photo-1451187580459-43490279c0fa?w=1920&q=80') center/cover no-repeat;
  transform: scale(1.1);
  animation: heroZoom 20s ease-in-out infinite alternate;
}

@keyframes heroZoom {
  0% { transform: scale(1.1); }
  100% { transform: scale(1); }
}

.hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(
    180deg,
    rgba(15, 23, 42, 0.7) 0%,
    rgba(15, 23, 42, 0.5) 50%,
    rgba(15, 23, 42, 0.85) 100%
  );
}

.hero-content-apple {
  position: relative;
  z-index: 2;
  text-align: center;
  max-width: 900px;
  padding: 0 24px;
}

.hero-badge-apple {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid rgba(255, 255, 255, 0.2);
  padding: 10px 20px;
  border-radius: 100px;
  font-size: 14px;
  font-weight: 500;
  color: rgba(255, 255, 255, 0.9);
  margin-bottom: 32px;
}

.hero-title-apple {
  font-size: clamp(40px, 8vw, 72px);
  font-weight: 800;
  line-height: 1.1;
  color: #fff;
  margin-bottom: 24px;
  letter-spacing: -0.02em;
}

.gradient-text {
  background: linear-gradient(135deg, #818CF8, #22D3EE, #F472B6);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc-apple {
  font-size: clamp(18px, 3vw, 22px);
  color: rgba(255, 255, 255, 0.8);
  max-width: 600px;
  margin: 0 auto 40px;
  line-height: 1.6;
}

.hero-actions-apple {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 60px;
}

.btn-apple {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 16px 32px;
  border-radius: 12px;
  font-size: 16px;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  border: none;
}

.btn-primary-apple {
  background: linear-gradient(135deg, #4F46E5, #7C3AED);
  color: #fff;
  box-shadow: 0 4px 20px rgba(79, 70, 229, 0.4);
}

.btn-primary-apple:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(79, 70, 229, 0.5);
}

.btn-secondary-apple {
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.btn-secondary-apple:hover {
  background: rgba(255, 255, 255, 0.2);
  transform: translateY(-3px);
}

.btn-outline-apple {
  background: transparent;
  color: var(--primary);
  border: 2px solid var(--primary);
  padding: 14px 28px;
}

.btn-outline-apple:hover {
  background: var(--primary);
  color: #fff;
}

/* ====== 统计卡片 ====== */
.hero-stats-apple {
  display: flex;
  gap: 24px;
  justify-content: center;
  flex-wrap: wrap;
}

.stat-card-apple {
  display: flex;
  align-items: center;
  gap: 16px;
  background: rgba(255, 255, 255, 0.08);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  padding: 20px 28px;
  border-radius: 16px;
  transition: all 0.3s ease;
}

.stat-card-apple:hover {
  background: rgba(255, 255, 255, 0.12);
  transform: translateY(-4px);
}

.stat-card-apple .stat-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background: linear-gradient(135deg, rgba(79, 70, 229, 0.3), rgba(6, 182, 212, 0.3));
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  color: #fff;
}

.stat-card-apple .stat-info {
  text-align: left;
}

.stat-card-apple .stat-num {
  font-size: 32px;
  font-weight: 800;
  color: #fff;
  display: block;
  line-height: 1;
}

.stat-card-apple .stat-label {
  font-size: 13px;
  color: rgba(255, 255, 255, 0.6);
  margin-top: 4px;
}

/* ====== 滚动指示器 ====== */
.scroll-indicator {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  color: rgba(255, 255, 255, 0.6);
  font-size: 24px;
  animation: bounce 2s ease-in-out infinite;
  cursor: pointer;
  z-index: 10;
}

@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50% { transform: translateX(-50%) translateY(10px); }
}

/* ====== 区块标题 - 苹果风格 ====== */
.section-header-apple {
  text-align: center;
  margin-bottom: 60px;
}

.section-tag-apple {
  display: inline-block;
  background: linear-gradient(135deg, rgba(79, 70, 229, 0.1), rgba(6, 182, 212, 0.1));
  color: var(--primary);
  padding: 8px 18px;
  border-radius: 100px;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 1.5px;
  margin-bottom: 20px;
}

.section-title-lg {
  font-size: clamp(32px, 5vw, 48px);
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.section-desc-lg {
  font-size: clamp(16px, 2vw, 20px);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* ====== 四大学科展示区 ====== */
.subjects-showcase {
  padding: 100px 0;
  background: var(--bg-body);
}

.subjects-grid-apple {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.subject-card-apple {
  position: relative;
  border-radius: 24px;
  overflow: hidden;
  height: 420px;
  cursor: pointer;
  transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.subject-card-apple:hover {
  transform: translateY(-10px);
  box-shadow: 0 25px 50px rgba(0, 0, 0, 0.15);
}

.subject-card-apple .subject-image {
  position: absolute;
  inset: 0;
}

.subject-card-apple .subject-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.6s ease;
}

.subject-card-apple:hover .subject-image img {
  transform: scale(1.1);
}

.subject-card-apple .subject-content {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 30px;
  background: linear-gradient(to top, rgba(0,0,0,0.9), transparent);
  color: #fff;
}

.subject-card-apple .subject-icon {
  width: 50px;
  height: 50px;
  border-radius: 14px;
  background: rgba(255, 255, 255, 0.2);
  backdrop-filter: blur(10px);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 22px;
  margin-bottom: 16px;
}

.subject-card-apple h3 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 8px;
}

.subject-card-apple p {
  font-size: 14px;
  opacity: 0.8;
  line-height: 1.5;
  margin-bottom: 12px;
}

.subject-link {
  color: #fff;
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  opacity: 0.9;
  transition: opacity 0.3s ease;
}

.subject-link:hover {
  opacity: 1;
}

/* ====== 教程板块 ====== */
.tutorials-section {
  padding: 100px 0;
  background: linear-gradient(180deg, var(--bg-body) 0%, var(--bg-section) 100%);
}

.tutorial-tabs {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-bottom: 48px;
  flex-wrap: wrap;
}

.tutorial-tab {
  padding: 12px 24px;
  border-radius: 100px;
  border: 2px solid var(--border-color);
  background: transparent;
  font-size: 15px;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.3s ease;
}

.tutorial-tab:hover,
.tutorial-tab.active {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.tutorials-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 28px;
}

.tutorial-card {
  background: var(--bg-card);
  border-radius: 20px;
  overflow: hidden;
  border: 1px solid var(--border-color);
  transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
}

.tutorial-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
  border-color: transparent;
}

.tutorial-image {
  position: relative;
  height: 180px;
  overflow: hidden;
}

.tutorial-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.tutorial-card:hover .tutorial-image img {
  transform: scale(1.08);
}

.tutorial-duration {
  position: absolute;
  top: 16px;
  right: 16px;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(10px);
  color: #fff;
  padding: 6px 12px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 6px;
}

.tutorial-body {
  padding: 24px;
}

.tutorial-meta {
  display: flex;
  gap: 10px;
  margin-bottom: 14px;
}

.tutorial-cat {
  padding: 5px 12px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 600;
}

.cat-geology { background: rgba(79, 70, 229, 0.1); color: #4F46E5; }
.cat-meteorology { background: rgba(5, 150, 105, 0.1); color: #059669; }
.cat-oceanography { background: rgba(6, 182, 212, 0.1); color: #0891B2; }
.cat-astronomy { background: rgba(139, 92, 246, 0.1); color: #7C3AED; }
.cat-comprehensive { background: rgba(217, 119, 6, 0.1); color: #D97706; }

.tutorial-level {
  padding: 5px 12px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 600;
}

.level-beginner { background: rgba(16, 185, 129, 0.1); color: #059669; }
.level-intermediate { background: rgba(245, 158, 11, 0.1); color: #D97706; }
.level-advanced { background: rgba(239, 68, 68, 0.1); color: #DC2626; }

.tutorial-card h3 {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 10px;
  line-height: 1.3;
}

.tutorial-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 16px;
}

.tutorial-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 16px;
  border-top: 1px solid var(--border-color);
}

.tutorial-footer span {
  font-size: 13px;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
}

.tutorial-link {
  font-size: 14px;
  font-weight: 600;
  color: var(--primary);
  text-decoration: none;
  transition: color 0.3s ease;
}

.tutorial-link:hover {
  color: var(--primary-dark);
}

.tutorials-more {
  text-align: center;
  margin-top: 48px;
}

/* ====== 特色功能展示区 ====== */
.feature-showcase {
  background: var(--bg-body);
}

.feature-item {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
  padding: 80px 0;
}

.feature-item.reverse {
  direction: rtl;
}

.feature-item.reverse > * {
  direction: ltr;
}

.feature-image {
  border-radius: 24px;
  overflow: hidden;
  box-shadow: 0 30px 60px rgba(0, 0, 0, 0.15);
}

.feature-image img {
  width: 100%;
  height: auto;
  display: block;
  transition: transform 0.6s ease;
}

.feature-item:hover .feature-image img {
  transform: scale(1.03);
}

.feature-content {
  padding: 40px;
}

.feature-tag {
  display: inline-block;
  background: linear-gradient(135deg, rgba(79, 70, 229, 0.1), rgba(6, 182, 212, 0.1));
  color: var(--primary);
  padding: 8px 16px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 2px;
  margin-bottom: 20px;
}

.feature-content h2 {
  font-size: clamp(32px, 4vw, 44px);
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 20px;
  letter-spacing: -0.02em;
}

.feature-content p {
  font-size: 18px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 28px;
}

.feature-list {
  list-style: none;
  margin-bottom: 32px;
}

.feature-list li {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 12px 0;
  font-size: 16px;
  color: var(--text-primary);
}

.feature-list li i {
  color: #10B981;
  font-size: 18px;
}

/* ====== 官方信息与大纲 ====== */
.official-section {
  padding: 100px 0;
  background: var(--bg-section);
}

.last-updated {
  margin-top: 16px;
  font-size: 14px;
  color: var(--text-secondary);
  font-weight: 500;
}

.last-updated time {
  color: var(--primary);
  font-weight: 700;
}

.official-disclaimer {
  display: flex;
  gap: 14px;
  align-items: flex-start;
  padding: 18px 20px;
  margin: 0 auto 36px;
  max-width: 920px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--primary);
  border-radius: 14px;
  color: var(--text-secondary);
  line-height: 1.65;
  font-size: 14px;
}

.official-disclaimer i {
  color: var(--primary);
  font-size: 20px;
  margin-top: 3px;
}

.official-disclaimer a {
  color: var(--primary);
  font-weight: 600;
}

.official-disclaimer code {
  font-size: 13px;
  background: rgba(79, 70, 229, 0.08);
  padding: 1px 6px;
  border-radius: 6px;
}

.official-facts {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
  margin-bottom: 48px;
}

.official-fact {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 24px;
}

.official-fact h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.official-fact h3 i {
  color: var(--primary);
  margin-right: 8px;
}

.official-fact p,
.official-fact li {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.official-fact ul {
  padding-left: 18px;
  margin: 0 0 8px;
}

.official-fact a {
  color: var(--primary);
}

.cite {
  font-size: 13px !important;
  color: var(--gray-400) !important;
  margin-top: 12px;
}

.official-subtitle {
  font-size: 24px;
  font-weight: 800;
  text-align: center;
  margin: 16px 0 12px;
  color: var(--text-primary);
}

.official-lead {
  text-align: center;
  max-width: 780px;
  margin: 0 auto 28px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.syllabus-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.syllabus-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 24px;
}

.syllabus-card h4 {
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--text-primary);
}

.syllabus-card p {
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-secondary);
}

.syllabus-cite {
  text-align: center;
  margin: 18px 0 40px;
}

.official-links {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 14px;
}

.official-link {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 16px 18px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 14px;
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 700;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.official-link small {
  font-weight: 500;
  color: var(--text-secondary);
}

.official-link:hover {
  transform: translateY(-3px);
  border-color: transparent;
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.08);
}

.resource-legal-note {
  max-width: 860px;
  margin: -12px auto 28px;
  text-align: center;
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.rbi-note,
.rbi-source {
  font-size: 12px;
  color: var(--gray-400);
  margin-top: 6px;
  line-height: 1.5;
}

.rbi-source {
  font-weight: 600;
}

@media (max-width: 768px) {
  .official-facts,
  .syllabus-grid {
    grid-template-columns: 1fr;
  }
  .official-section {
    padding: 60px 0;
  }
}

/* ====== 资源板块 ====== */
.resources-section {
  padding: 100px 0;
  background: var(--bg-section);
}

.resource-filters {
  display: flex;
  gap: 16px;
  margin-bottom: 40px;
  flex-wrap: wrap;
  justify-content: center;
}

.resource-filters select {
  padding: 12px 20px;
  border-radius: 12px;
  border: 2px solid var(--border-color);
  background: var(--bg-card);
  font-size: 15px;
  font-weight: 500;
  color: var(--text-primary);
  cursor: pointer;
  transition: all 0.3s ease;
  min-width: 140px;
}

.resource-filters select:hover,
.resource-filters select:focus {
  border-color: var(--primary);
  outline: none;
}

.resource-search {
  position: relative;
  flex: 1;
  max-width: 300px;
}

.resource-search i {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
}

.resource-search input {
  width: 100%;
  padding: 12px 16px 12px 44px;
  border-radius: 12px;
  border: 2px solid var(--border-color);
  background: var(--bg-card);
  font-size: 15px;
  color: var(--text-primary);
  transition: all 0.3s ease;
}

.resource-search input:focus {
  border-color: var(--primary);
  outline: none;
}

.resource-grid-apple {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

/* ====== 教材推荐区 ====== */
.textbooks-section {
  margin-top: 80px;
}

.textbooks-title {
  font-size: 28px;
  font-weight: 800;
  text-align: center;
  margin-bottom: 40px;
  color: var(--text-primary);
}

.textbooks-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

.textbook-card {
  background: var(--bg-card);
  border-radius: 20px;
  padding: 32px;
  border: 1px solid var(--border-color);
  transition: all 0.3s ease;
  position: relative;
}

.textbook-card:hover {
  transform: translateY(-6px);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.08);
  border-color: transparent;
}

.textbook-card .textbook-rank {
  font-size: 36px;
  margin-bottom: 16px;
}

.textbook-card h4 {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.textbook-author {
  font-size: 14px;
  color: var(--primary);
  font-weight: 600;
  margin-bottom: 12px;
}

.textbook-desc {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ====== 学习路线图 ====== */
.roadmap-section {
  padding: 100px 0;
  background: var(--bg-body);
}

.roadmap-timeline {
  max-width: 800px;
  margin: 0 auto;
  position: relative;
  padding: 20px;
}

.roadmap-step {
  display: flex;
  gap: 24px;
  padding: 32px;
  background: var(--bg-card);
  border-radius: 20px;
  border: 1px solid var(--border-color);
  margin-bottom: 20px;
  transition: all 0.3s ease;
  position: relative;
}

.roadmap-step:hover {
  transform: translateX(8px);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
  border-color: var(--primary-light);
}

.step-number {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  font-weight: 800;
  flex-shrink: 0;
}

.step-content {
  flex: 1;
}

.step-badge {
  display: inline-block;
  padding: 6px 14px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 700;
  margin-bottom: 12px;
}

.step-badge.beginner {
  background: rgba(16, 185, 129, 0.1);
  color: #059669;
}

.step-badge.intermediate {
  background: rgba(245, 158, 11, 0.1);
  color: #D97706;
}

.step-badge.advanced {
  background: rgba(239, 68, 68, 0.1);
  color: #DC2626;
}

.step-badge.competition {
  background: linear-gradient(135deg, rgba(79, 70, 229, 0.1), rgba(6, 182, 212, 0.1));
  color: var(--primary);
}

.step-content h4 {
  font-size: 20px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.step-content p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 12px;
}

.step-time {
  font-size: 13px;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
}

.roadmap-line {
  width: 3px;
  height: 30px;
  background: linear-gradient(to bottom, var(--primary-light), var(--border-color));
  margin-left: 42px;
  border-radius: 2px;
}

/* ====== 响应式设计 - 苹果风格 ====== */
@media (max-width: 1024px) {
  .subjects-grid-apple {
    grid-template-columns: repeat(2, 1fr);
  }

  .feature-item {
    grid-template-columns: 1fr;
    gap: 40px;
    padding: 60px 0;
  }

  .feature-item.reverse {
    direction: ltr;
  }

  .feature-image {
    max-width: 500px;
    margin: 0 auto;
  }
}

@media (max-width: 768px) {
  /* 英雄区 */
  .hero-apple {
    min-height: auto;
    padding: 100px 0 60px;
  }

  .hero-bg-image {
    animation: none;
  }

  .hero-title-apple {
    font-size: 32px;
    line-height: 1.2;
  }

  .hero-desc-apple {
    font-size: 16px;
    padding: 0 10px;
  }

  .hero-stats-apple {
    flex-direction: column;
    align-items: center;
    gap: 12px;
    width: 100%;
    padding: 0 16px;
  }

  .stat-card-apple {
    width: 100%;
    max-width: 100%;
    padding: 16px 20px;
  }

  .stat-card-apple .stat-icon {
    width: 40px;
    height: 40px;
    font-size: 18px;
  }

  .stat-card-apple .stat-num {
    font-size: 24px;
  }

  /* 学科展示 */
  .subjects-showcase {
    padding: 60px 0;
  }

  .subjects-grid-apple {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .subject-card-apple {
    height: 280px;
  }

  .subject-card-apple .subject-content {
    padding: 20px;
  }

  .subject-card-apple h3 {
    font-size: 20px;
  }

  .subject-card-apple p {
    font-size: 13px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
  }

  /* 教程板块 */
  .tutorials-section {
    padding: 60px 0;
  }

  .tutorials-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .tutorial-tabs {
    gap: 6px;
    padding: 0 8px;
    overflow-x: auto;
    flex-wrap: nowrap;
    justify-content: flex-start;
    -webkit-overflow-scrolling: touch;
    padding-bottom: 8px;
  }

  .tutorial-tab {
    padding: 10px 16px;
    font-size: 13px;
    white-space: nowrap;
    flex-shrink: 0;
  }

  .tutorial-image {
    height: 160px;
  }

  .tutorial-body {
    padding: 18px;
  }

  .tutorial-card h3 {
    font-size: 16px;
  }

  .tutorial-card p {
    font-size: 13px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
  }

  .tutorial-meta {
    flex-wrap: wrap;
    gap: 6px;
  }

  /* 区块标题 */
  .section-header-apple {
    margin-bottom: 40px;
    padding: 0 16px;
  }

  .section-title-lg {
    font-size: 28px;
    line-height: 1.2;
  }

  .section-desc-lg {
    font-size: 15px;
  }

  /* 特色功能 */
  .feature-item {
    padding: 40px 0;
  }

  .feature-content {
    padding: 20px 16px;
  }

  .feature-content h2 {
    font-size: 26px;
  }

  .feature-content p {
    font-size: 15px;
  }

  .feature-list li {
    font-size: 14px;
    padding: 10px 0;
  }

  /* 资源板块 */
  .resources-section {
    padding: 60px 0;
  }

  .resource-filters {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
    padding: 0 16px;
  }

  .resource-filters select {
    width: 100%;
    font-size: 14px;
    padding: 14px 16px;
  }

  .resource-search {
    max-width: 100%;
  }

  .resource-search input {
    font-size: 14px;
    padding: 14px 16px 14px 44px;
  }

  .resource-grid-apple {
    grid-template-columns: 1fr;
    gap: 16px;
    padding: 0 16px;
  }

  /* 教材 */
  .textbooks-section {
    margin-top: 40px;
    padding: 0 16px;
  }

  .textbooks-title {
    font-size: 22px;
    margin-bottom: 24px;
  }

  .textbooks-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .textbook-card {
    padding: 24px;
  }

  .textbook-card .textbook-rank {
    font-size: 28px;
    margin-bottom: 12px;
  }

  .textbook-card h4 {
    font-size: 16px;
  }

  /* 学习路线图 */
  .roadmap-section {
    padding: 60px 0;
  }

  .roadmap-step {
    flex-direction: column;
    gap: 16px;
    padding: 24px;
  }

  .step-number {
    width: 48px;
    height: 48px;
    font-size: 20px;
  }

  .step-content h4 {
    font-size: 18px;
  }

  .roadmap-line {
    margin-left: 34px;
    height: 20px;
  }

  /* 题库 */
  .quiz-section {
    padding: 60px 0;
  }

  .quiz-category-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
  }

  .quiz-cat-btn {
    padding: 16px 12px;
  }

  .qcat-icon {
    width: 44px;
    height: 44px;
    font-size: 18px;
  }

  .qcat-name {
    font-size: 14px;
  }

  .qcat-count {
    font-size: 12px;
  }

  .quiz-stats-bar {
    flex-direction: column;
    gap: 12px;
    padding: 16px;
  }

  .mock-exam-entry p {
    font-size: 13px;
  }

  /* 社区 */
  .community-section {
    padding: 60px 0;
  }

  .community-tabs {
    gap: 8px;
  }

  .community-tab {
    padding: 8px 16px;
    font-size: 13px;
  }

  .community-toolbar {
    flex-direction: column;
    gap: 12px;
  }

  .community-search {
    width: 100%;
  }

  .community-search input {
    width: 100%;
  }

  .community-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  /* 页脚 */
  .footer {
    padding: 40px 0 0;
  }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 24px;
  }

  .footer-brand {
    grid-column: 1 / -1;
    text-align: center;
  }

  .footer-links {
    text-align: center;
  }
}

@media (max-width: 480px) {
  /* 容器 */
  .container {
    padding: 0 14px;
  }

  /* 英雄区 */
  .hero-apple {
    padding: 80px 0 40px;
  }

  .hero-badge-apple {
    font-size: 11px;
    padding: 6px 12px;
    gap: 6px;
  }

  .hero-title-apple {
    font-size: 26px;
    padding: 0 8px;
  }

  .hero-desc-apple {
    font-size: 14px;
    margin-bottom: 24px;
  }

  .hero-actions-apple {
    flex-direction: column;
    width: 100%;
    padding: 0 16px;
    gap: 12px;
  }

  .btn-apple {
    width: 100%;
    justify-content: center;
    padding: 14px 24px;
    font-size: 15px;
  }

  .stat-card-apple {
    padding: 14px 18px;
    gap: 12px;
  }

  .stat-card-apple .stat-icon {
    width: 36px;
    height: 36px;
    font-size: 16px;
  }

  .stat-card-apple .stat-num {
    font-size: 22px;
  }

  .stat-card-apple .stat-label {
    font-size: 11px;
  }

  .scroll-indicator {
    display: none;
  }

  /* 学科 */
  .subject-card-apple {
    height: 240px;
  }

  .subject-card-apple .subject-icon {
    width: 40px;
    height: 40px;
    font-size: 18px;
  }

  /* 教程 */
  .section-title-lg {
    font-size: 24px;
  }

  .tutorial-card h3 {
    font-size: 15px;
  }

  .tutorial-duration {
    font-size: 11px;
    padding: 4px 10px;
  }

  .tutorial-footer {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }

  .tutorial-link {
    font-size: 13px;
  }

  /* 特色功能 */
  .feature-content h2 {
    font-size: 22px;
  }

  .feature-tag {
    font-size: 11px;
    padding: 6px 12px;
  }

  /* 题库 */
  .quiz-category-grid {
    grid-template-columns: 1fr 1fr;
    gap: 10px;
  }

  .quiz-cat-btn {
    padding: 14px 10px;
  }

  .qcat-icon {
    width: 40px;
    height: 40px;
    font-size: 16px;
  }

  /* 页脚 */
  .footer-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .footer-bottom {
    font-size: 12px;
    padding: 16px 0;
  }

  /* 模态框 */
  .modal {
    padding: 20px 16px;
    border-radius: 16px;
    margin: 10px;
  }

  .modal-close {
    width: 32px;
    height: 32px;
    top: 12px;
    right: 12px;
  }
}

/* ====== 触控设备优化 ====== */
@media (hover: none) and (pointer: coarse) {
  .subject-card-apple:hover {
    transform: none;
  }

  .subject-card-apple:active {
    transform: scale(0.98);
  }

  .tutorial-card:hover {
    transform: none;
  }

  .tutorial-card:active {
    transform: scale(0.98);
  }

  .textbook-card:hover {
    transform: none;
  }

  .btn-apple:hover {
    transform: none;
  }

  .btn-apple:active {
    transform: scale(0.96);
  }

  .stat-card-apple:hover {
    transform: none;
  }

  .feature-image img {
    transition: none;
  }

  .feature-item:hover .feature-image img {
    transform: none;
  }
}

/* ====== 小屏幕横屏优化 ====== */
@media (max-height: 500px) and (orientation: landscape) {
  .hero-apple {
    min-height: auto;
    padding: 60px 0 40px;
  }

  .hero-stats-apple {
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: center;
  }

  .stat-card-apple {
    padding: 12px 16px;
  }
}

/* ====== 安全区域适配（iPhone X 系列） ====== */
@supports (padding-bottom: env(safe-area-inset-bottom)) {
  .footer-bottom {
    padding-bottom: calc(16px + env(safe-area-inset-bottom));
  }

  .modal {
    padding-bottom: calc(20px + env(safe-area-inset-bottom));
  }
}

/* ====== 减少动画（用户偏好） ====== */
@media (prefers-reduced-motion: reduce) {
  .hero-bg-image {
    animation: none;
  }

  .scroll-indicator {
    animation: none;
  }

  .fade-in {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .subject-card-apple,
  .tutorial-card,
  .textbook-card,
  .btn-apple,
  .stat-card-apple {
    transition: none;
  }
}

/* ====== 脉冲动画 ====== */
@keyframes pulse {
  0% {
    box-shadow: 0 0 0 0 rgba(79, 70, 229, 0.4);
  }
  70% {
    box-shadow: 0 0 0 10px rgba(79, 70, 229, 0);
  }
  100% {
    box-shadow: 0 0 0 0 rgba(79, 70, 229, 0);
  }
}

/* ====== 夜间模式调整 ====== */
[data-theme="dark"] .hero-bg-image {
  filter: brightness(0.7);
}

[data-theme="dark"] .subject-card-apple .subject-content {
  background: linear-gradient(to top, rgba(0,0,0,0.95), transparent);
}

[data-theme="dark"] .tutorial-card {
  background: var(--bg-card);
}

[data-theme="dark"] .feature-showcase {
  background: var(--bg-body);
}

[data-theme="dark"] .textbook-card {
  background: var(--bg-card);
}

/* ====== 脉冲动画类 - 用于按钮触发的滚动反馈 ====== */
.pulse-animation {
  animation: pulse 0.6s ease-out !important;
}