/* ============================================================
 * ClassDemo · 样式
 * 浅色蓝调 · 卡片面板 · 桌面三栏 / 移动单栏
 * ============================================================ */

:root {
  --blue: #2563eb;
  --blue-hi: #3b82f6;
  --blue-deep: #1d4ed8;
  --ink: #0f2742;
  --ink-2: #3b5773;
  --ink-3: #6d849c;
  --ink-4: #93a8bd;
  --line: rgba(23, 62, 105, 0.1);
  --line-soft: rgba(23, 62, 105, 0.06);
  --card: #ffffff;
  --radius: 20px;
  --shadow: 0 1px 2px rgba(255, 255, 255, 0.9) inset, 0 8px 24px rgba(48, 105, 166, 0.09);
  --shadow-hi: 0 1px 2px rgba(255, 255, 255, 0.9) inset, 0 18px 40px rgba(48, 105, 166, 0.17);
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  color: var(--ink);
  background: #f4f9fd;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* 背景光斑 */
.bg-wash {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background:
    radial-gradient(1100px 560px at 8% -8%, #d8e9fb 0%, rgba(216, 233, 251, 0) 62%),
    radial-gradient(900px 520px at 96% 2%, #e2f1fe 0%, rgba(226, 241, 254, 0) 58%),
    radial-gradient(1200px 700px at 50% 108%, #e8f1fb 0%, rgba(232, 241, 251, 0) 60%),
    linear-gradient(180deg, #f8fbfe 0%, #eef4fb 100%);
}

a { color: inherit; }

img { max-width: 100%; }

/* ---------------- 顶栏 ---------------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 60;
  background: rgba(250, 253, 255, 0.84);
  backdrop-filter: blur(16px) saturate(1.25);
  -webkit-backdrop-filter: blur(16px) saturate(1.25);
  border-bottom: 1px solid var(--line-soft);
}

.topbar-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  gap: 22px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 13px;
  text-decoration: none;
  color: var(--ink);
  flex: none;
}

.logo-img {
  display: block;
  height: 29px;
  width: auto;
  flex: none;
}

.logo-sub {
  font-size: 12px;
  line-height: 1;
  color: var(--ink-3);
  letter-spacing: 0.02em;
  padding-left: 13px;
  border-left: 1px solid var(--line);
  white-space: nowrap;
}

.nav {
  display: flex;
  gap: 4px;
}

.nav a {
  padding: 8px 16px;
  border-radius: 999px;
  font-size: 14px;
  color: var(--ink-2);
  text-decoration: none;
  transition: background 0.16s, color 0.16s;
  white-space: nowrap;
}

.nav a:hover { background: rgba(255, 255, 255, 0.8); color: var(--ink); }

.nav a.active {
  background: #fff;
  color: var(--blue);
  font-weight: 600;
  border: 1px solid var(--line-soft);
  box-shadow: 0 2px 8px rgba(48, 105, 166, 0.1);
}

.topbar-right {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 10px;
}

.topbar-note {
  font-size: 12.5px;
  color: var(--ink-3);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  border: none;
  border-radius: 11px;
  padding: 9px 17px;
  font-size: 14px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  text-decoration: none;
  transition: transform 0.14s, box-shadow 0.16s, background 0.16s;
  white-space: nowrap;
}

.btn-primary {
  color: #fff;
  background: linear-gradient(180deg, var(--blue-hi), var(--blue));
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.26);
}

.btn-primary:hover { box-shadow: 0 9px 22px rgba(37, 99, 235, 0.34); transform: translateY(-1px); }

.btn-ghost {
  color: var(--ink-2);
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: 0 2px 8px rgba(48, 105, 166, 0.06);
}

.btn-ghost:hover { color: var(--blue); border-color: rgba(37, 99, 235, 0.28); }

/* ---------------- 通用容器 ---------------- */
.wrap {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 24px;
}

/* 注意：只设 padding-top，不能用 padding 简写，
   否则会覆盖 .wrap 的左右内边距，导致区块贴边、与 hero 不对齐 */
.section { padding-top: 46px; }

.section-head {
  display: flex;
  align-items: baseline;
  gap: 14px;
  margin-bottom: 20px;
}

.section-head h2 {
  margin: 0;
  font-size: 22px;
  letter-spacing: -0.01em;
}

.section-head .sub {
  font-size: 13px;
  color: var(--ink-3);
}

.section-head .more {
  margin-left: auto;
  font-size: 13.5px;
  color: var(--blue);
  text-decoration: none;
  font-weight: 600;
}

.section-head .more:hover { text-decoration: underline; }

/* ---------------- 首页 Hero ---------------- */
.hero {
  max-width: 1400px;
  margin: 0 auto;
  padding: 54px 24px 10px;
  display: grid;
  grid-template-columns: 1.02fr 0.98fr;
  gap: 60px;
  align-items: center;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 12.5px;
  letter-spacing: 0.1em;
  color: #3470bd;
  background: rgba(255, 255, 255, 0.86);
  border: 1px solid rgba(37, 99, 235, 0.16);
  padding: 6px 13px;
  border-radius: 999px;
}

.eyebrow i {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: #22c55e;
  box-shadow: 0 0 0 3px rgba(34, 197, 94, 0.16);
  display: block;
}

.hero h1 {
  font-size: clamp(31px, 3.9vw, 50px);
  line-height: 1.16;
  letter-spacing: -0.025em;
  margin: 20px 0 18px;
  font-weight: 700;
}

.hero h1 em {
  font-style: normal;
  color: var(--blue);
  position: relative;
}

.hero p.lead {
  margin: 0 0 26px;
  font-size: 15px;
  line-height: 1.85;
  color: var(--ink-2);
  max-width: 560px;
}

/* 搜索条 */
.searchbar {
  display: flex;
  align-items: center;
  gap: 8px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 15px;
  padding: 6px 6px 6px 16px;
  box-shadow: var(--shadow);
  max-width: 540px;
  transition: border-color 0.16s, box-shadow 0.16s;
}

.searchbar:focus-within {
  border-color: rgba(37, 99, 235, 0.42);
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1), var(--shadow);
}

.searchbar .icon {
  color: var(--ink-4);
  flex: none;
  display: grid;
  place-items: center;
}

.searchbar input {
  flex: 1;
  min-width: 0;
  border: none;
  outline: none;
  background: transparent;
  font-family: inherit;
  font-size: 14.5px;
  color: var(--ink);
  padding: 10px 0;
}

.searchbar input::placeholder { color: var(--ink-4); }

.searchbar .btn { padding: 10px 20px; border-radius: 11px; }

.hero-stats {
  display: flex;
  gap: 26px;
  margin-top: 26px;
  flex-wrap: wrap;
}

.hero-stats div { display: flex; flex-direction: column; gap: 3px; }

.hero-stats strong {
  font-size: 21px;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.hero-stats span { font-size: 12px; color: var(--ink-3); }

/* Hero 右侧预览（扑克牌手风琴扇形） */
.hero-visual { position: relative; }

.hero-visual::before {
  content: "";
  position: absolute;
  inset: 4% 2% 10% 4%;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.28) 0%, rgba(59, 130, 246, 0) 68%);
  filter: blur(26px);
  z-index: 0;
}

.hero-fan {
  position: relative;
  z-index: 1;
  height: 470px;
  display: block;
}

.fan-card {
  position: absolute;
  left: 50%;
  bottom: 26px;
  width: 300px;
  transform-origin: 50% 100%;
  transform: translateX(calc(-50% + var(--dx))) rotate(var(--angle));
  z-index: var(--z, 1);
  border-radius: 16px;
  border: 6px solid #fff;
  background: #fff;
  box-shadow: 0 24px 50px -20px rgba(17, 52, 96, 0.45), 0 0 0 1px rgba(23, 62, 105, 0.06);
  transition: transform 0.55s cubic-bezier(0.22, 1, 0.36, 1), box-shadow 0.55s;
  text-decoration: none;
  overflow: hidden;
  cursor: pointer;
}

.fan-card.is-main { width: 330px; }

.fan-card img { width: 100%; display: block; aspect-ratio: 760 / 428; object-fit: cover; }

.fan-label {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 10px 13px;
  font-size: 13.5px;
  font-weight: 600;
  color: var(--ink);
  background: #fff;
}

.fan-new {
  font-style: normal;
  font-size: 10.5px;
  font-weight: 700;
  color: #fff;
  background: var(--blue);
  padding: 2px 8px;
  border-radius: 999px;
  letter-spacing: 0.02em;
}

/* hover 手风琴拉开 */
.hero-fan:hover .fan-card { transform: translateX(calc(-50% + var(--dx) * 1.24)) rotate(calc(var(--angle) * 1.35)); }
.fan-card:hover {
  transform: translateX(calc(-50% + var(--dx) * 1.24)) rotate(calc(var(--angle) * 1.35)) translateY(-12px);
  z-index: 30;
  box-shadow: 0 34px 70px -22px rgba(17, 52, 96, 0.55), 0 0 0 1px rgba(23, 62, 105, 0.08);
}

/* 没有任何已上线课件时的主推位占位（正常不会出现） */
.hero-card {
  position: relative;
  z-index: 1;
  border-radius: 20px;
  overflow: hidden;
  border: 7px solid #fff;
  box-shadow: 0 34px 70px -24px rgba(17, 52, 96, 0.5), 0 0 0 1px rgba(23, 62, 105, 0.06);
  cursor: pointer;
}

.hero-empty {
  display: flex;
  align-items: center;
  justify-content: center;
  aspect-ratio: 760 / 428;
  font-size: 14px;
  color: var(--ink-3);
  background: var(--soft, #f4f9fd);
}

.float-tag {
  position: absolute;
  z-index: 40;
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(23, 62, 105, 0.08);
  border-radius: 12px;
  padding: 8px 13px;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--ink);
  box-shadow: 0 12px 28px -8px rgba(17, 52, 96, 0.28);
  display: flex;
  align-items: center;
  gap: 7px;
}

.float-tag b { color: var(--blue); font-weight: 700; }
.float-tag.fan-tag { top: 0; right: 2px; }

/* ---------------- 年级宫格 ---------------- */
.grade-grid {
  display: grid;
  grid-template-columns: repeat(6, minmax(0, 1fr));
  gap: 14px;
}

.grade-card {
  position: relative;
  display: block;
  background: #fff;
  border: 1px solid var(--line-soft);
  border-radius: 17px;
  padding: 20px 14px 17px;
  text-align: center;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
  transition: transform 0.18s, box-shadow 0.18s, border-color 0.18s;
  overflow: hidden;
}

.grade-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-hi);
  border-color: rgba(37, 99, 235, 0.24);
}

.grade-card .big {
  display: block;
  font-size: 25px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
}

.grade-card .gbadge {
  position: absolute;
  top: 9px;
  right: 9px;
  font-size: 10px;
  font-weight: 700;
  color: #fff;
  background: var(--blue);
  border-radius: 999px;
  padding: 2px 7px;
  line-height: 1.6;
}

.grade-card .meta {
  display: block;
  font-size: 12px;
  color: var(--ink-3);
  margin-top: 7px;
}

.grade-card .bar {
  display: block;
  height: 3px;
  border-radius: 99px;
  background: rgba(23, 62, 105, 0.07);
  margin-top: 13px;
  overflow: hidden;
}

.grade-card .bar i {
  display: block;
  height: 100%;
  border-radius: 99px;
  background: linear-gradient(90deg, #60a5fa, #2563eb);
}

.grade-card.is-empty { opacity: 0.68; }
.grade-card.is-empty:hover { opacity: 1; }

/* ---------------- 科目宫格 ---------------- */
.subject-grid {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 14px;
}

.subject-card {
  display: flex;
  align-items: center;
  gap: 13px;
  background: #fff;
  border: 1px solid var(--line-soft);
  border-radius: 17px;
  padding: 17px 16px;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
  transition: transform 0.18s, box-shadow 0.18s, border-color 0.18s;
}

.subject-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-hi);
  border-color: rgba(37, 99, 235, 0.2);
}

.subject-glyph {
  width: 42px;
  height: 42px;
  flex: none;
  border-radius: 13px;
  display: grid;
  place-items: center;
  font-size: 17px;
  font-weight: 700;
  color: #fff;
  letter-spacing: 0;
}

.subject-card .sc-body { min-width: 0; }

.subject-card .sc-name {
  display: block;
  font-size: 15px;
  font-weight: 600;
  line-height: 1.3;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.subject-card .sc-meta {
  display: block;
  font-size: 12px;
  color: var(--ink-3);
  margin-top: 3px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* ---------------- 课件卡片 ---------------- */
.course-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
}

.course-card {
  background: #fff;
  border: 1px solid rgba(255, 255, 255, 0.95);
  border-radius: var(--radius);
  padding: 8px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  transition: transform 0.2s, box-shadow 0.2s;
}

.course-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hi); }

.course-thumb {
  position: relative;
  border-radius: 14px;
  overflow: hidden;
  aspect-ratio: 16 / 9;
  background: #e4edf6;
}

.course-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
  transition: transform 0.5s cubic-bezier(0.22, 1, 0.36, 1);
}

.course-card:hover .course-thumb img { transform: scale(1.03); }

/* 封面角标 */
.badge {
  position: absolute;
  top: 10px;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 11.5px;
  font-weight: 600;
  padding: 4px 9px;
  border-radius: 8px;
  line-height: 1.5;
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
}

.badge.left { left: 10px; }
.badge.right { right: 10px; }

.badge.live {
  color: #fff;
  background: rgba(37, 99, 235, 0.9);
}

.badge.plan {
  color: #fff;
  background: rgba(15, 39, 66, 0.68);
}

.badge.new {
  color: #fff;
  background: linear-gradient(180deg, #f87362, #e2483a);
  box-shadow: 0 4px 12px rgba(226, 72, 58, 0.3);
}

.badge.free {
  color: #0f7a56;
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid rgba(18, 137, 107, 0.2);
}

/* 筹备中占位 */
.course-thumb.is-plan {
  display: grid;
  place-items: center;
  position: relative;
}

.course-thumb.is-plan::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image: linear-gradient(rgba(23, 62, 105, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(23, 62, 105, 0.03) 1px, transparent 1px);
  background-size: 22px 22px;
  mask-image: radial-gradient(circle at 50% 50%, #000 20%, transparent 78%);
  -webkit-mask-image: radial-gradient(circle at 50% 50%, #000 20%, transparent 78%);
}

.plan-glyph {
  position: relative;
  z-index: 1;
  font-size: 40px;
  font-weight: 700;
  opacity: 0.34;
  letter-spacing: 0.02em;
}

.course-body {
  padding: 14px 12px 4px;
  display: flex;
  flex-direction: column;
  gap: 7px;
  flex: 1;
}

.course-chapter {
  font-size: 12px;
  color: var(--ink-3);
  letter-spacing: 0.01em;
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.course-chapter .dot {
  width: 3px;
  height: 3px;
  border-radius: 50%;
  background: var(--ink-4);
  display: inline-block;
}

.course-title {
  margin: 0;
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.4;
}

.course-desc {
  margin: 0;
  font-size: 13px;
  line-height: 1.68;
  color: var(--ink-2);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.course-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 1px;
}

.tag {
  font-size: 11.5px;
  color: #3470bd;
  background: #eff6ff;
  padding: 3px 8px;
  border-radius: 6px;
  line-height: 1.5;
  white-space: nowrap;
}

.course-cta { padding: 12px 12px 8px; }

.btn-open {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  width: 100%;
  padding: 11px 14px;
  border: none;
  border-radius: 12px;
  font-family: inherit;
  font-size: 14px;
  font-weight: 600;
  color: #fff;
  background: linear-gradient(180deg, var(--blue-hi), var(--blue));
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.24);
  cursor: pointer;
  text-decoration: none;
  transition: box-shadow 0.18s, transform 0.14s;
}

.btn-open:hover { box-shadow: 0 9px 22px rgba(37, 99, 235, 0.32); transform: translateY(-1px); }

.btn-open .arrow { transition: transform 0.18s; }
.btn-open:hover .arrow { transform: translateX(3px); }

.btn-open.is-disabled {
  background: #eff3f8;
  color: #96a9bc;
  box-shadow: none;
  cursor: not-allowed;
}

.btn-open.is-disabled:hover { transform: none; box-shadow: none; }

/* ---------------- 怎么用 ---------------- */
.howto {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}

.howto-item {
  background: #fff;
  border: 1px solid var(--line-soft);
  border-radius: 18px;
  padding: 22px 22px 24px;
  box-shadow: var(--shadow);
}

.howto-item .step {
  display: inline-block;
  font-size: 11.5px;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--blue);
  background: #eff6ff;
  padding: 3px 9px;
  border-radius: 6px;
}

.howto-item strong {
  display: block;
  margin: 13px 0 8px;
  font-size: 16px;
  letter-spacing: -0.01em;
}

.howto-item p {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.78;
  color: var(--ink-3);
}

@media (max-width: 1180px) {
  .howto { grid-template-columns: minmax(0, 1fr); }
}

/* ---------------- 课件库 ---------------- */
.library {
  max-width: 1400px;
  margin: 0 auto;
  padding: 30px 24px 0;
  display: grid;
  grid-template-columns: 268px minmax(0, 1fr);
  gap: 26px;
  align-items: start;
}

.filters {
  position: sticky;
  top: 88px;
  background: #fff;
  border: 1px solid var(--line-soft);
  border-radius: 18px;
  padding: 18px 16px 16px;
  box-shadow: var(--shadow);
}

.filter-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 4px;
}

.filter-head strong { font-size: 14px; }

.filter-reset {
  border: none;
  background: none;
  font-family: inherit;
  font-size: 12.5px;
  color: var(--ink-3);
  cursor: pointer;
  padding: 3px 6px;
  border-radius: 6px;
}

.filter-reset:hover { color: var(--blue); background: #f2f7fd; }

.filter-block { padding: 14px 0 2px; border-top: 1px solid var(--line-soft); margin-top: 12px; }

.filter-block:first-of-type { border-top: none; margin-top: 4px; }

.filter-label {
  font-size: 11.5px;
  letter-spacing: 0.1em;
  color: var(--ink-4);
  margin-bottom: 9px;
  font-weight: 600;
}

.chips { display: flex; flex-wrap: wrap; gap: 6px; }

/* 等宽网格排布：让换行后的每一行都对齐 */
.chips.cols-4 { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); }
.chips.cols-3 { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); }
.chips.cols-2 { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); }

.chips.cols-4 .chip,
.chips.cols-3 .chip,
.chips.cols-2 .chip {
  text-align: center;
  overflow: hidden;
  text-overflow: ellipsis;
  padding-left: 6px;
  padding-right: 6px;
}

.chip {
  border: 1px solid transparent;
  background: #f4f8fc;
  color: var(--ink-2);
  font-family: inherit;
  font-size: 13px;
  padding: 6px 12px;
  border-radius: 9px;
  cursor: pointer;
  transition: all 0.15s;
  line-height: 1.5;
  white-space: nowrap;
}

.chip:hover { background: #e9f1fa; color: var(--ink); }

.chip.active {
  background: var(--blue);
  color: #fff;
  font-weight: 600;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.24);
}

.chip .n {
  font-size: 11px;
  opacity: 0.65;
  margin-left: 3px;
}

/* 结果区 */
.results { min-width: 0; }

.crumbs {
  font-size: 12.5px;
  color: var(--ink-3);
  display: flex;
  align-items: center;
  gap: 7px;
  flex-wrap: wrap;
}

.crumbs a { text-decoration: none; color: var(--ink-3); }
.crumbs a:hover { color: var(--blue); }
.crumbs .sep { color: var(--ink-4); }

.results-head {
  display: flex;
  align-items: flex-end;
  gap: 14px;
  margin: 10px 0 18px;
  flex-wrap: wrap;
}

.results-head h1 {
  margin: 0;
  font-size: 25px;
  letter-spacing: -0.02em;
}

.results-count {
  font-size: 13px;
  color: var(--ink-3);
  margin-left: auto;
  padding-bottom: 4px;
}

.results-bar {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 18px;
  flex-wrap: wrap;
}

.results-bar .searchbar { flex: 1 1 340px; max-width: none; }

.mobile-filter-btn { display: none; }

.empty {
  background: rgba(255, 255, 255, 0.72);
  border: 1px dashed rgba(23, 62, 105, 0.16);
  border-radius: 18px;
  padding: 54px 30px;
  text-align: center;
}

.empty .icon {
  width: 52px;
  height: 52px;
  border-radius: 15px;
  background: #eef5fc;
  display: grid;
  place-items: center;
  margin: 0 auto 16px;
  color: #8fb0cf;
}

.empty h3 { margin: 0 0 8px; font-size: 16px; }

.empty p { margin: 0 auto; font-size: 13.5px; color: var(--ink-3); line-height: 1.75; max-width: 420px; }

.empty .btn { margin-top: 18px; }

/* ---------------- 播放页 ---------------- */
.play {
  max-width: 1600px;
  margin: 0 auto;
  padding: 16px 22px 22px;
}

.play-bar {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 6px 2px 14px;
  flex-wrap: wrap;
}

.play-bar .back {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  font-size: 13.5px;
  color: var(--ink-2);
  text-decoration: none;
  padding: 8px 13px;
  border-radius: 10px;
  background: #fff;
  border: 1px solid var(--line-soft);
  box-shadow: 0 2px 8px rgba(48, 105, 166, 0.06);
  transition: color 0.15s, border-color 0.15s;
}

.play-bar .back:hover { color: var(--blue); border-color: rgba(37, 99, 235, 0.28); }

.play-title { min-width: 0; }

.play-title h1 {
  margin: 0;
  font-size: 17px;
  letter-spacing: -0.01em;
  line-height: 1.3;
}

.play-title .meta {
  font-size: 12.5px;
  color: var(--ink-3);
  margin-top: 2px;
}

.play-actions { margin-left: auto; display: flex; gap: 9px; }

.play-stage {
  position: relative;
  height: calc(100vh - 152px);
  min-height: 540px;
  border-radius: 18px;
  overflow: hidden;
  background: #0a1420;
  border: 1px solid rgba(23, 62, 105, 0.14);
  box-shadow: 0 24px 60px -24px rgba(17, 52, 96, 0.44);
}

.play-stage iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}

.play-loading {
  position: absolute;
  inset: 0;
  z-index: 2;
  display: grid;
  place-items: center;
  gap: 14px;
  background: linear-gradient(160deg, #0d1a28, #101f30);
  color: #cfe2f5;
  transition: opacity 0.4s;
}

.play-loading.is-hidden { opacity: 0; pointer-events: none; }

.play-loading .box { text-align: center; }

.spinner {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  border: 2.5px solid rgba(255, 255, 255, 0.16);
  border-top-color: #6ea8f0;
  animation: spin 0.8s linear infinite;
  margin: 0 auto 14px;
}

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

.play-loading .t { font-size: 14px; letter-spacing: 0.02em; }
.play-loading .s { font-size: 12px; color: #7f97ae; margin-top: 6px; }

.play-note {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  color: var(--ink-3);
  padding: 12px 4px 0;
  flex-wrap: wrap;
}

/* ---------------- 页脚 ---------------- */
.footer {
  max-width: 1400px;
  margin: 64px auto 0;
  padding: 26px 24px 46px;
  border-top: 1px solid var(--line-soft);
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  align-items: flex-start;
  font-size: 12.5px;
  color: var(--ink-3);
  line-height: 1.8;
}

.footer .f-brand { display: flex; align-items: center; gap: 10px; font-weight: 600; color: var(--ink-2); }

.footer .f-brand img { display: block; height: 16px; width: auto; }

.footer .f-brand .f-sub {
  font-size: 12px;
  color: var(--ink-3);
  padding-left: 10px;
  border-left: 1px solid var(--line);
  white-space: nowrap;
}

.footer p { margin: 0; max-width: 640px; }

.footer .f-right { margin-left: auto; text-align: right; }

/* ---------------- 抽屉（移动端筛选） ---------------- */
.drawer-mask {
  position: fixed;
  inset: 0;
  background: rgba(15, 39, 66, 0.42);
  backdrop-filter: blur(2px);
  z-index: 80;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.22s;
}

.drawer-mask.open { opacity: 1; pointer-events: auto; }

/* ---------------- 响应式 ---------------- */
@media (max-width: 1180px) {
  .hero { grid-template-columns: 1fr; gap: 38px; padding-top: 44px; }
  .hero-visual { max-width: 660px; margin: 0 auto; }

  .course-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .subject-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .grade-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}

@media (max-width: 960px) {
  .library {
    grid-template-columns: minmax(0, 1fr);
    padding-top: 18px;
  }

  /* 侧栏改为抽屉 */
  .filters {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    width: min(320px, 86vw);
    z-index: 90;
    border-radius: 0 18px 18px 0;
    overflow-y: auto;
    transform: translateX(-104%);
    transition: transform 0.26s cubic-bezier(0.22, 1, 0.36, 1);
    box-shadow: 0 20px 60px rgba(15, 39, 66, 0.3);
    border: none;
  }

  .filters.open { transform: translateX(0); }

  .mobile-filter-btn { display: inline-flex; }

  .play-stage { height: calc(100vh - 176px); min-height: 420px; }
}

@media (max-width: 720px) {
  .topbar-inner { height: 58px; padding: 0 14px; gap: 12px; }

  .logo-sub { display: none; }
  .logo-img { height: 23px; }

  .nav { gap: 2px; overflow-x: auto; scrollbar-width: none; }
  .nav::-webkit-scrollbar { display: none; }
  .nav a { padding: 7px 11px; font-size: 13px; }

  .topbar-note { display: none; }
  .topbar-right .btn-primary { padding: 8px 13px; font-size: 13px; }

  .wrap { padding: 0 15px; }

  .hero { padding: 28px 15px 4px; gap: 26px; }
  .hero h1 { font-size: 29px; margin: 16px 0 14px; }
  .hero p.lead { font-size: 14px; line-height: 1.8; }
  .hero-stats { gap: 18px; margin-top: 20px; }
  .hero-stats strong { font-size: 18px; }

  /* 扑克牌扇形整体缩小，适配窄屏 */
  .hero-fan { height: 300px; transform: scale(0.62); transform-origin: top center; margin-bottom: -96px; }
  .fan-tag { top: -6px; right: 0; }

  .section { padding-top: 32px; }
  .section-head { margin-bottom: 15px; gap: 9px; }
  .section-head h2 { font-size: 18px; }
  .section-head .sub { display: none; }

  .grade-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 9px; }
  .grade-card { padding: 14px 8px 12px; border-radius: 14px; }
  .grade-card .big { font-size: 19px; }
  .grade-card .meta { font-size: 11px; margin-top: 5px; }
  .grade-card .bar { margin-top: 9px; }
  .grade-card .gbadge { font-size: 9px; padding: 1px 5px; }

  .subject-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 9px; }
  .subject-card { padding: 12px 11px; gap: 10px; border-radius: 14px; }
  .subject-glyph { width: 34px; height: 34px; border-radius: 10px; font-size: 14px; }
  .subject-card .sc-name { font-size: 14px; }
  .subject-card .sc-meta { font-size: 11px; }

  .course-grid { grid-template-columns: minmax(0, 1fr); gap: 16px; }

  .library { padding: 14px 15px 0; gap: 16px; }
  .results-head h1 { font-size: 20px; }
  .results-count { margin-left: 0; width: 100%; padding-bottom: 0; }

  .play { padding: 10px 12px 16px; }
  .play-bar { gap: 9px; padding-bottom: 10px; }
  .play-title { order: 3; flex: 1 1 100%; }
  .play-actions { margin-left: auto; }
  .play-actions .btn { padding: 8px 12px; font-size: 13px; }
  .play-stage { height: calc(100vh - 210px); min-height: 380px; border-radius: 14px; }

  .footer { margin-top: 40px; padding: 22px 15px 34px; }
  .footer .f-right { margin-left: 0; text-align: left; }
}

@media (max-width: 400px) {
  .nav a { padding: 6px 9px; font-size: 12.5px; }
  .hero h1 { font-size: 26px; }
}