/* ══════════════════════════════════════════════════
   自学平台 — 学生端交互增强样式
   ══════════════════════════════════════════════════ */

/* ── 分区标题 ── */
.section-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 1.5rem;
  margin-bottom: 1.6rem;
}
.section-head h2 {
  margin: 0;
  font-family: var(--font-heading);
  font-size: clamp(2rem, 4vw, 3rem);
  letter-spacing: 0.08em;
  white-space: nowrap;
}
.section-head p {
  max-width: 380px;
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
  line-height: 1.7;
  text-align: right;
}

/* ── 功能卡片网格 ── */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.3rem;
}

/* ── 功能卡片 ── */
.feature-card {
  --card-accent: var(--accent);
  --card-bg: var(--bg2);
  position: relative;
  min-height: 210px;
  padding: 1.6rem 1.5rem 3.2rem;
  border: 2px solid transparent;
  border-radius: 1.4rem;
  background: var(--card-bg);
  box-shadow: 0 6px 24px rgba(0,0,0,0.06), 0 1px 4px rgba(0,0,0,0.04);
  overflow: hidden;
  transition: all 280ms cubic-bezier(0.4, 0, 0.2, 1);
  backdrop-filter: blur(6px);
}
.feature-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: var(--card-accent);
  border-radius: 1.4rem 1.4rem 0 0;
  opacity: 0;
  transition: opacity 280ms ease;
}
.feature-card:hover {
  transform: translateY(-6px);
  box-shadow: 0 18px 42px rgba(0,0,0,0.12), 0 4px 12px rgba(0,0,0,0.06);
  border-color: var(--card-accent);
}
.feature-card:hover::before {
  opacity: 1;
}
.feature-card::after {
  content: attr(data-mark);
  position: absolute;
  right: 0.4rem;
  bottom: -1.5rem;
  color: var(--card-accent);
  font-family: var(--font-heading);
  font-size: 6.5rem;
  line-height: 1;
  opacity: 0.06;
  pointer-events: none;
  transition: opacity 280ms ease;
}
.feature-card:hover::after {
  opacity: 0.12;
}
.feature-card h3 {
  position: relative;
  z-index: 1;
  margin: 0;
  color: var(--card-accent);
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.04em;
}
.feature-card p {
  position: relative;
  z-index: 1;
  margin: 0.5rem 0 0;
  color: var(--ink);
  line-height: 1.65;
  font-size: 0.95rem;
  font-weight: 500;
}
.feature-card a {
  position: absolute;
  left: 1.5rem;
  bottom: 1.5rem;
  z-index: 1;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  background: var(--card-accent);
  color: #fff;
  font-family: var(--font-ui);
  font-weight: 700;
  font-size: 0.88rem;
  text-decoration: none;
  transition: all 200ms ease;
}
.feature-card a:hover {
  transform: scale(1.06);
  box-shadow: 0 4px 14px rgba(0,0,0,0.2);
}
.feature-card a::after {
  content: "→";
  font-size: 1.1em;
  transition: transform 200ms ease;
}
.feature-card:hover a::after {
  transform: translateX(3px);
}

/* ── 卡片图标 ── */
.card-icon {
  position: relative;
  z-index: 1;
  font-size: 2rem;
  margin-bottom: 0.5rem;
  line-height: 1;
}

/* ── 卡片进度条 ── */
.card-progress {
  position: relative;
  z-index: 1;
  height: 4px;
  margin: 0.8rem 0 0;
  background: rgba(0,0,0,0.06);
  border-radius: 2px;
  overflow: hidden;
}
.card-progress-fill {
  height: 100%;
  background: var(--card-accent);
  border-radius: 2px;
  transition: width 400ms ease;
}

/* ── 知识点卡片增强 ── */
.kaodian-card {
  transition: box-shadow 200ms ease;
}

.kaodian-card:hover {
  box-shadow: 0 6px 24px rgba(43,29,21,0.1);
}

/* ── 阅读材料段落增强 ── */
.passage p {
  text-indent: 2em;
  margin-bottom: 0.5rem;
}

/* ── 答案动画 ── */
.answer-box {
  transition: all 300ms ease;
  overflow: hidden;
}

.answer-box.show {
  animation: fadeSlideIn 300ms ease;
}

@keyframes fadeSlideIn {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ── 加载状态 ── */
.practice-loading {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 2rem 1rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.practice-loading::before {
  content: '';
  width: 1.2rem;
  height: 1.2rem;
  border: 2px solid var(--panel-border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ── 错题标记按钮 ── */
.btn-mark-wrong {
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--accent);
  border-radius: 999px;
  font-family: var(--font-ui);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--accent);
  background: transparent;
  cursor: pointer;
  transition: all 180ms ease;
}

.btn-mark-wrong:hover {
  color: #fff;
  background: var(--accent);
}

.btn-mark-wrong.marked {
  color: #fff;
  background: var(--accent);
}

/* ── 提示信息 ── */
.tooltip {
  position: relative;
  display: inline-block;
  cursor: help;
  border-bottom: 1px dashed var(--muted);
}

.tooltip::after {
  content: attr(data-tip);
  position: absolute;
  bottom: 100%;
  left: 50%;
  transform: translateX(-50%);
  padding: 0.4rem 0.8rem;
  background: var(--ink);
  color: var(--bg2);
  font-size: 0.78rem;
  border-radius: 0.4rem;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 180ms ease;
}

.tooltip:hover::after {
  opacity: 1;
}

/* ── 进度条 ── */
.progress-bar {
  width: 100%;
  height: 6px;
  background: var(--filter-bg);
  border-radius: 3px;
  overflow: hidden;
  margin: 0.5rem 0;
}

.progress-bar .fill {
  height: 100%;
  background: var(--accent);
  border-radius: 3px;
  transition: width 400ms ease;
}

/* ── 徽章 ── */
.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.4rem;
  height: 1.4rem;
  padding: 0 0.35rem;
  border-radius: 999px;
  font-size: 0.7rem;
  font-weight: 700;
  color: #fff;
  background: var(--accent);
}

/* ── 空状态 ── */
.empty-state {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--muted);
}

.empty-state .icon {
  font-size: 2.5rem;
  margin-bottom: 0.8rem;
  opacity: 0.4;
}

.empty-state .text {
  font-size: 0.9rem;
}
/* ── 占位页面(建设中) ── */
.page-placeholder {
  max-width: 800px;
  margin: 4rem auto;
  padding: 3rem 2rem;
  text-align: center;
  background: var(--bg2);
  border: 1px solid var(--rule);
  border-radius: 8px;
}
.page-placeholder .icon {
  font-size: 4rem;
  margin-bottom: 1rem;
}
.page-placeholder h1 {
  font-family: var(--font-heading);
  font-size: 2rem;
  color: var(--accent);
  margin-bottom: 0.5rem;
}
.page-placeholder p {
  color: var(--text);
  font-size: 1.05rem;
  margin-bottom: 1.5rem;
}
.page-placeholder .back-link {
  display: inline-block;
  padding: 0.5rem 1.2rem;
  color: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 6px;
  text-decoration: none;
  font-size: 0.9rem;
  transition: background 0.2s, color 0.2s;
}
.page-placeholder .back-link:hover {
  background: var(--accent);
  color: #fff;
}

/* === 学科内导航移动端菜单 (2026-07-31) === */
/* 桌面端隐藏移动菜单按钮 */
.mobile-menu{display:none!important;}
@media(max-width:640px){
  .mobile-menu{
    display:inline-flex;align-items:center;justify-content:center;
    background:var(--accent,#9f2d20);color:#fff;border:none;
    border-radius:0.5rem;padding:0.45rem 0.9rem;
    font-size:0.85rem;font-family:var(--font-ui,sans-serif);
    font-weight:600;cursor:pointer;white-space:nowrap;
    transition:background 180ms ease;
  }
  .mobile-menu.active{background:var(--accent2,#b98a36);}
  .nav-inner{position:relative;}
  .nav-links{
    display:none !important;position:absolute;top:100%;left:0;right:0;
    flex-direction:column;background:var(--bg2,#fff8ea);
    border-bottom:1px solid var(--rule,#d7b98c);
    box-shadow:0 4px 12px rgba(0,0,0,0.12);
    padding:0.5rem;z-index:200;gap:0.2rem;
  }
  .nav-links.open{display:flex !important;}
  .nav-links a{display:block;width:100%;padding:0.6rem 0.8rem;text-align:center;border-radius:0.4rem;}
  .nav-links li{display:block;width:100%;}
  .nav-links ul{list-style:none;padding:0;margin:0;}
}