:root {
  --ink: #22304a;
  --ink-soft: #66748c;
  --forest: #5b9cf5;
  --forest-2: #3b82f6;
  --mint: #dbeafe;
  --cream: #f7faff;
  --paper: #ffffff;
  --line: #dfe5ef;
  --red: #b43c3c;
  --amber: #9a6518;
  --shadow: 0 18px 60px rgba(59, 130, 246, 0.11);
  --radius: 22px;
}

* { box-sizing: border-box; font-family: "Microsoft YaHei", "微软雅黑", sans-serif !important; }
html { color-scheme: light; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--cream);
  font-family: "Microsoft YaHei", "微软雅黑", sans-serif;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
button, input, textarea, select { font: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
img { display: block; max-width: 100%; }
[hidden] { display: none !important; }

.page-container { width: min(1180px, calc(100% - 48px)); margin: 0 auto; }
.site-header {
  position: sticky; top: 0; z-index: 40;
  height: 72px; padding: 0 34px;
  display: flex; align-items: center; justify-content: space-between;
  color: var(--ink); background: rgba(255, 254, 250, 0.94);
  border-bottom: 1px solid rgba(23, 32, 51, 0.1); backdrop-filter: blur(18px);
}
.brand, .login-brand { display: inline-flex; align-items: center; gap: 12px; font-weight: 750; letter-spacing: -.02em; }
.brand-mark {
  display: grid; width: 34px; height: 34px; place-items: center;
  color: #f7f5ed; background: var(--forest); border-radius: 11px;
  font-size: 18px;
}
.brand-mark-large { width: 46px; height: 46px; font-size: 25px; background: var(--mint); color: var(--forest); }
.top-nav { display: flex; align-items: center; gap: 22px; font-size: 14px; }
.top-nav > a { color: #405047; transition: color .2s; }
.top-nav > a:hover { color: var(--forest-2); }
.user-chip { display: inline-flex; align-items: center; gap: 8px; padding: 8px 12px; border: 1px solid var(--line); border-radius: 999px; background: white; font-weight: 650; }
.status-dot { width: 7px; height: 7px; border-radius: 50%; background: #42a675; box-shadow: 0 0 0 3px #dff4e7; }
.inline-form { display: inline; margin: 0; }
.nav-button { padding: 0; border: 0; color: #68736d; background: none; cursor: pointer; }

.flash-stack { position: fixed; top: 86px; left: 50%; z-index: 100; width: min(560px, calc(100% - 32px)); transform: translateX(-50%); pointer-events: none; }
.flash { margin-bottom: 8px; padding: 13px 16px; color: #18412f; background: #e7f7ed; border: 1px solid #bfe6ce; border-radius: 12px; box-shadow: var(--shadow); transition: opacity .3s, transform .3s; }
.flash-error { color: #7a2424; background: #fff0f0; border-color: #f0c0c0; }
.flash-warning { color: #6d4813; background: #fff7e5; border-color: #edd29d; }
.flash-hide { opacity: 0; transform: translateY(-8px); }

.button { display: inline-flex; min-height: 44px; padding: 10px 18px; align-items: center; justify-content: center; gap: 9px; border: 1px solid transparent; border-radius: 12px; font-weight: 700; cursor: pointer; transition: transform .18s, background .18s, border-color .18s; }
.button:hover { transform: translateY(-1px); }
.button-primary { color: white; background: var(--forest-2); box-shadow: 0 8px 20px rgba(59, 130, 246, .22); }
.button-primary:hover { background: var(--forest-2); }
.button-ghost { color: var(--ink); background: transparent; border-color: var(--line); }
.button-light { color: var(--forest); background: white; }
.button-large { width: 100%; min-height: 54px; margin-top: 5px; justify-content: space-between; padding-inline: 20px; }
.muted { color: #738078; }

/* Login */
.login-page { min-height: 100vh; background: var(--paper); }
.login-shell { min-height: 100vh; display: grid; grid-template-columns: minmax(430px, .92fr) minmax(520px, 1.08fr); }
.login-intro { position: relative; overflow: hidden; display: flex; min-height: 100vh; padding: 50px 7vw 54px; flex-direction: column; justify-content: space-between; color: white; background: var(--forest); }
.login-intro::before, .login-intro::after { content: ""; position: absolute; border-radius: 50%; border: 1px solid rgba(167, 227, 193, .15); }
.login-intro::before { width: 620px; height: 620px; right: -310px; top: 9%; box-shadow: 0 0 0 80px rgba(158, 197, 255, .035), 0 0 0 160px rgba(158, 197, 255, .025); }
.login-intro::after { width: 240px; height: 240px; left: -120px; bottom: -80px; }
.login-brand, .intro-copy, .intro-security { position: relative; z-index: 1; }
.intro-copy { max-width: 560px; }
.intro-copy h1 { margin: 18px 0 22px; font-size: clamp(48px, 6vw, 78px); font-weight: 700; line-height: 1.08; letter-spacing: -.045em; }
.intro-copy p { max-width: 440px; color: rgba(255,255,255,.7); font-size: 17px; }
.login-panel { display: flex; padding: 50px 24px 30px; align-items: center; justify-content: center; flex-direction: column; background: #fbfaf6; }
.login-card { width: min(430px, 100%); padding: 42px; background: white; border: 1px solid #e8e8e2; border-radius: 26px; box-shadow: var(--shadow); }
.login-kicker { color: var(--forest-2); font-size: 13px; font-weight: 750; }
.login-card h2 { margin: 8px 0 3px; font-size: 32px; font-weight: 700; letter-spacing: -.025em; }
.stack-form { display: grid; gap: 18px; margin-top: 28px; }
.stack-form label, .admin-form label { display: grid; gap: 8px; font-size: 14px; font-weight: 700; }
.stack-form input, .admin-form input, .admin-form textarea, .admin-form select {
  width: 100%; min-height: 48px; padding: 11px 13px; color: var(--ink); background: #fbfbf8;
  border: 1px solid #d9ddd8; border-radius: 10px; outline: none; transition: border-color .18s, box-shadow .18s;
}
.admin-form textarea { resize: vertical; }
.stack-form input:focus, .admin-form input:focus, .admin-form textarea:focus, .admin-form select:focus { border-color: #4a8c6f; box-shadow: 0 0 0 3px rgba(74,140,111,.12); }
.stack-form small, .admin-form small { color: #7d8781; font-size: 12px; font-weight: 450; }
.login-help { margin-top: 26px; padding-top: 20px; display: flex; align-items: center; justify-content: space-between; border-top: 1px solid #ecece7; color: #7a847f; font-size: 12px; }
.login-help strong { color: var(--forest); }

/* Library */
.library-page { padding-block: 70px 90px; }
.welcome-row { display: flex; margin-bottom: 46px; align-items: end; justify-content: space-between; gap: 30px; }
.welcome-row h1 { margin: 9px 0 8px; font-size: clamp(32px, 4vw, 46px); font-weight: 700; letter-spacing: -.035em; }
.welcome-row p { margin: 0; color: var(--ink-soft); }
.course-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 26px; }
.course-card { overflow: hidden; background: var(--paper); border: 1px solid #e0e1da; border-radius: var(--radius); box-shadow: 0 10px 40px rgba(29,48,39,.055); transition: transform .22s, box-shadow .22s; }
.course-card:hover { transform: translateY(-5px); box-shadow: var(--shadow); }
.course-cover { position: relative; display: block; aspect-ratio: 16/10; overflow: hidden; background: #dbe9df; }
.course-cover img { width: 100%; height: 100%; object-fit: cover; transition: transform .5s; }
.course-card:hover .course-cover img { transform: scale(1.035); }
.cover-placeholder { display: grid; width: 100%; height: 100%; place-items: center; background: linear-gradient(140deg, #cddfff, #eef4ff 65%, #b8d2ff); }
.cover-placeholder::after { content: ""; position: absolute; width: 120px; height: 120px; border: 1px solid rgba(23,70,162,.18); border-radius: 50%; box-shadow: 0 0 0 35px rgba(23,70,162,.03), 0 0 0 70px rgba(23,70,162,.025); }
.cover-placeholder span { z-index: 1; color: var(--forest); font-size: 70px; font-weight: 700; }
.course-card-body { padding: 24px; }
.course-meta { display: flex; gap: 7px; color: #7c8781; font-size: 11px; text-transform: uppercase; letter-spacing: .04em; }
.course-card h2 { margin: 10px 0 9px; font-size: 22px; line-height: 1.3; }
.course-card-body > p { min-height: 46px; margin: 0; display: -webkit-box; overflow: hidden; color: #68746d; font-size: 13px; -webkit-box-orient: vertical; -webkit-line-clamp: 2; }
.course-card-footer { margin-top: 22px; padding-top: 16px; display: flex; align-items: center; justify-content: space-between; gap: 16px; border-top: 1px solid #e8edf5; color: #707b8e; font-size: 12px; }
.course-progress { min-width: 0; flex: 1; display: grid; gap: 7px; }
.course-progress progress, .table-progress progress { width: 100%; height: 6px; overflow: hidden; appearance: none; border: 0; border-radius: 999px; background: #e5ecf8; }
.course-progress progress::-webkit-progress-bar, .table-progress progress::-webkit-progress-bar { background: #e5ecf8; border-radius: 999px; }
.course-progress progress::-webkit-progress-value, .table-progress progress::-webkit-progress-value { background: var(--forest-2); border-radius: 999px; }
.course-progress progress::-moz-progress-bar, .table-progress progress::-moz-progress-bar { background: var(--forest-2); border-radius: 999px; }
.circle-link { display: grid; width: 34px; height: 34px; place-items: center; color: white; background: var(--forest); border-radius: 50%; font-size: 18px; }
.empty-state { padding: 90px 30px; text-align: center; background: rgba(255,255,255,.5); border: 1px dashed #cbd1cb; border-radius: 24px; }
.empty-icon { display: grid; width: 58px; height: 58px; margin: 0 auto 18px; place-items: center; color: var(--forest); background: #e0eee5; border-radius: 18px; font-size: 26px; }
.empty-state h2 { margin: 0 0 7px; font-size: 27px; }
.empty-state p { margin: 0 0 20px; color: #758079; }
.empty-state.compact { padding: 45px; }

/* Course detail */
.course-hero { color: white; background: var(--forest); }
.course-hero-inner { min-height: 430px; padding-block: 60px; display: grid; grid-template-columns: 1.25fr .75fr; align-items: center; gap: 70px; }
.back-link { display: inline-block; margin-bottom: 40px; color: rgba(255,255,255,.65); font-size: 13px; }
.course-hero h1 { max-width: 760px; margin: 12px 0 18px; font-size: clamp(40px, 5vw, 62px); font-weight: 700; line-height: 1.12; letter-spacing: -.04em; }
.course-hero-copy > p { max-width: 700px; margin: 0; color: rgba(255,255,255,.68); }
.hero-stats { margin-top: 35px; display: flex; gap: 36px; color: rgba(255,255,255,.6); font-size: 12px; }
.hero-stats strong { margin-right: 5px; color: white; font-size: 17px; }
.course-hero-art { position: relative; overflow: hidden; aspect-ratio: 4/3; display: grid; place-items: center; background: linear-gradient(145deg, rgba(167,227,193,.26), rgba(255,255,255,.05)); border: 1px solid rgba(255,255,255,.15); border-radius: 28px; box-shadow: 0 35px 70px rgba(0,0,0,.16); transform: rotate(2deg); }
.course-hero-art::after { content: ""; position: absolute; inset: 18px; border: 1px solid rgba(255,255,255,.13); border-radius: 20px; }
.course-hero-art img { width: 100%; height: 100%; object-fit: cover; }
.hero-letter { color: var(--mint); font-size: 120px; font-weight: 700; }
.syllabus-section { padding-block: 70px 100px; }
.section-heading { margin-bottom: 25px; display: flex; align-items: end; justify-content: space-between; }
.section-heading h2 { margin: 5px 0 0; font-size: 34px; }
.section-note { color: #79837d; font-size: 12px; }
.syllabus-list { display: grid; gap: 18px; }
.chapter-block { overflow: hidden; background: var(--paper); border: 1px solid var(--line); border-radius: 18px; }
.chapter-header { padding: 22px 25px; display: flex; align-items: center; gap: 17px; background: #f0f1eb; border-bottom: 1px solid var(--line); }
.chapter-number { display: grid; width: 42px; height: 42px; place-items: center; color: white; background: var(--forest); border-radius: 12px; }
.chapter-header h3, .chapter-header p { margin: 0; }
.chapter-header h3 { font-size: 16px; }
.chapter-header p { margin-top: 2px; color: #7a847f; font-size: 11px; }
.lesson-row { padding: 17px 25px; display: grid; grid-template-columns: 38px 1fr auto 28px; align-items: center; gap: 13px; border-bottom: 1px solid #ecece7; transition: background .18s; }
.lesson-row:last-child { border-bottom: 0; }
.lesson-row:hover { background: #f7faf7; }
.play-dot { display: grid; width: 31px; height: 31px; place-items: center; color: var(--forest); background: #e0eee5; border-radius: 50%; font-size: 10px; }
.lesson-name { display: grid; gap: 2px; }
.lesson-name strong { font-size: 14px; }
.lesson-name small, .lesson-duration { color: #89918c; font-size: 11px; }
.lesson-arrow { color: var(--forest-2); font-size: 18px; }
.lesson-empty { padding: 22px; color: #879089; text-align: center; font-size: 13px; }

/* Player */
.player-page { background: #0b1120; }
.player-page .site-header { color: #edf3ff; background: rgba(11,17,32,.96); border-color: rgba(255,255,255,.1); }
.player-page .brand-mark { color: var(--forest); background: var(--mint); }
.player-page .top-nav > a, .player-page .nav-button { color: rgba(255,255,255,.67); }
.player-page .user-chip { color: white; background: rgba(255,255,255,.06); border-color: rgba(255,255,255,.12); }
.player-layout { height: calc(100vh - 72px); display: grid; grid-template-columns: minmax(0, 1fr) 350px; }
.video-column { min-width: 0; overflow-y: auto; padding: 28px 32px 30px; }
.player-heading { margin-bottom: 20px; display: flex; align-items: end; justify-content: space-between; gap: 30px; color: white; }
.player-heading a, .player-heading p { color: rgba(255,255,255,.55); font-size: 12px; }
.player-heading h1 { margin: 4px 0 2px; font-size: 27px; font-weight: 700; }
.player-heading p { margin: 0; }
.video-stage { position: relative; overflow: hidden; aspect-ratio: 16/9; max-height: calc(100vh - 230px); background: #020403; border: 1px solid rgba(255,255,255,.1); border-radius: 14px; box-shadow: 0 25px 70px rgba(0,0,0,.35); }
.video-stage video { width: 100%; height: 100%; display: block; object-fit: contain; }
.player-message { position: absolute; inset: 0; z-index: 5; display: flex; align-items: center; justify-content: center; flex-direction: column; gap: 13px; color: white; background: #060a14; }
.player-message strong { font-size: 14px; }
.player-error span { max-width: 520px; color: rgba(255,255,255,.63); font-size: 12px; text-align: center; }
.spinner { width: 31px; height: 31px; border: 2px solid rgba(255,255,255,.2); border-top-color: var(--mint); border-radius: 50%; animation: spin .8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.watermark-layer { position: absolute; inset: 0; z-index: 4; overflow: hidden; pointer-events: none; }
.moving-watermark { position: absolute; left: -38%; padding: 3px 6px; color: rgba(255,255,255,.16); font-size: clamp(9px, .75vw, 11px); letter-spacing: .02em; white-space: nowrap; text-shadow: 0 1px 2px rgba(0,0,0,.35); animation: watermark-roll 46s linear infinite; }
.moving-watermark:nth-child(1) { top: 24%; animation-duration: 52s; }
.moving-watermark:nth-child(2) { top: 72%; animation-delay: -24s; animation-duration: 58s; }
@keyframes watermark-roll { from { transform: translateX(0); } to { transform: translateX(155vw); } }
.player-toolbar { margin-top: 16px; display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.player-toolbar a { min-width: 0; padding: 13px 15px; display: grid; gap: 3px; color: rgba(255,255,255,.8); background: rgba(255,255,255,.05); border: 1px solid rgba(255,255,255,.09); border-radius: 10px; transition: background .18s, border-color .18s; }
.player-toolbar a:hover { background: rgba(61,130,246,.14); border-color: rgba(158,197,255,.3); }
.player-toolbar small { color: rgba(255,255,255,.4); font-size: 10px; }
.player-toolbar strong { overflow: hidden; font-size: 12px; text-overflow: ellipsis; white-space: nowrap; }
.player-toolbar .next-lesson { text-align: right; }
.outline-panel { overflow: hidden; color: white; background: #111a2d; border-left: 1px solid rgba(255,255,255,.09); }
.outline-title { height: 64px; padding: 0 20px; display: flex; align-items: center; justify-content: space-between; border-bottom: 1px solid rgba(255,255,255,.08); }
.outline-title span { font-size: 17px; font-weight: 700; }
.outline-title strong { color: rgba(255,255,255,.45); font-size: 10px; }
.outline-scroll { height: calc(100% - 64px); overflow-y: auto; padding: 8px 10px 30px; scrollbar-width: thin; }
.outline-chapter { padding: 18px 10px 7px; color: rgba(255,255,255,.38); font-size: 10px; font-weight: 750; letter-spacing: .04em; }
.outline-lesson { padding: 12px 10px; display: grid; grid-template-columns: 24px 1fr; gap: 8px; align-items: flex-start; color: rgba(255,255,255,.65); border-radius: 9px; font-size: 12px; }
.outline-lesson:hover { background: rgba(255,255,255,.04); }
.outline-lesson.active { color: white; background: rgba(167,227,193,.1); }
.outline-play { color: var(--mint); font-size: 10px; }
.outline-lesson span:last-child { display: grid; gap: 3px; }
.outline-lesson small { color: rgba(255,255,255,.35); font-size: 9px; }

/* Forms and errors */
.narrow-page { width: min(620px, calc(100% - 40px)); margin: 0 auto; padding: 70px 0 90px; }
.form-page-heading { margin-bottom: 25px; }
.form-page-heading h1 { margin: 7px 0 4px; font-size: 36px; }
.form-page-heading p { margin: 0; color: var(--ink-soft); }
.form-card { padding: 32px; background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.error-page { min-height: calc(100vh - 72px); padding: 80px 24px; display: flex; align-items: center; justify-content: center; flex-direction: column; text-align: center; }
.error-code { color: #c7d8f5; font-size: 104px; font-weight: 700; line-height: 1; }
.error-page h1 { max-width: 700px; margin: 18px 0 5px; font-size: 31px; }
.error-page p { margin: 0 0 25px; color: #778179; }

/* Admin */
.admin-page { background: #f2f3ee; }
.admin-layout { min-height: calc(100vh - 72px); display: grid; grid-template-columns: 235px minmax(0, 1fr); }
.admin-sidebar { position: sticky; top: 72px; height: calc(100vh - 72px); padding: 28px 18px; display: flex; flex-direction: column; background: var(--forest); color: white; }
.admin-label { padding: 0 13px 18px; color: rgba(255,255,255,.42); font-size: 10px; font-weight: 800; letter-spacing: .15em; }
.admin-sidebar nav { display: grid; gap: 5px; }
.admin-sidebar nav a { padding: 11px 13px; display: flex; align-items: center; gap: 11px; color: rgba(255,255,255,.67); border-radius: 9px; font-size: 13px; }
.admin-sidebar nav a:hover, .admin-sidebar nav a.active { color: white; background: rgba(255,255,255,.09); }
.admin-sidebar nav a span { width: 18px; color: var(--mint); text-align: center; }
.admin-main { min-width: 0; padding: 42px clamp(24px, 4vw, 60px) 70px; }
.admin-heading { margin-bottom: 28px; display: flex; align-items: end; justify-content: space-between; gap: 30px; }
.admin-heading h1 { margin: 6px 0 2px; font-size: 36px; letter-spacing: -.025em; }
.admin-heading p { margin: 0; color: #6d7871; font-size: 13px; }
.dark-link { margin-bottom: 9px; color: #76817a; }
.notice { margin-bottom: 24px; padding: 15px 18px; display: flex; align-items: center; gap: 13px; color: #6f4a12; background: #fff8e7; border: 1px solid #edd6a5; border-radius: 12px; font-size: 12px; }
.notice span { flex: 1; color: #806638; }
.notice a { font-weight: 800; }
.stat-grid { margin-bottom: 24px; display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.stat-grid article { padding: 22px; background: var(--paper); border: 1px solid var(--line); border-radius: 16px; }
.stat-grid span, .stat-grid small { display: block; color: #78827c; font-size: 11px; }
.stat-grid strong { display: block; margin: 10px 0 2px; color: var(--forest); font-size: 34px; line-height: 1; }
.admin-card { background: var(--paper); border: 1px solid var(--line); border-radius: 18px; box-shadow: 0 8px 30px rgba(29,48,39,.04); }
.card-heading { padding: 22px 24px; border-bottom: 1px solid var(--line); }
.card-heading h2 { margin: 0 0 2px; font-size: 16px; }
.card-heading p { margin: 0; color: #818a84; font-size: 11px; }
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 12px; }
th { padding: 13px 18px; color: #7e8882; background: #f3f4ef; font-size: 10px; text-align: left; text-transform: uppercase; letter-spacing: .04em; white-space: nowrap; }
td { padding: 15px 18px; border-top: 1px solid #e9eae5; vertical-align: middle; }
tbody tr:first-child td { border-top: 0; }
tbody tr:hover { background: #fafbf7; }
.align-right { text-align: right; }
.table-empty { padding: 50px; color: #879089; text-align: center; }
.tag { display: inline-flex; padding: 4px 7px; color: #496457; background: #e5eee8; border-radius: 6px; font-size: 9px; font-weight: 750; }
.tag-purple { color: #604f7e; background: #ece7f5; }
.status { display: inline-flex; align-items: center; gap: 5px; color: #7d8781; font-size: 10px; }
.status::before { content: ""; width: 6px; height: 6px; background: #aeb5b0; border-radius: 50%; }
.status.active { color: #2e7754; }
.status.active::before { background: #45a573; box-shadow: 0 0 0 3px #e0f2e7; }
.identity-cell, .course-cell { display: flex; align-items: center; gap: 11px; }
.identity-cell > div, .course-cell > div { display: grid; gap: 2px; }
.identity-cell small, .course-cell small { color: #89918c; font-size: 10px; }
.avatar { display: grid; min-width: 34px; height: 34px; place-items: center; color: var(--forest); background: #dfece4; border-radius: 10px; font-weight: 800; }
.mini-cover { overflow: hidden; width: 54px; height: 38px; display: grid; place-items: center; color: var(--forest); background: #e1ebff; border-radius: 7px; font-size: 18px; }
.mini-cover img { width: 100%; height: 100%; object-fit: cover; }
.actions { white-space: nowrap; }
.actions a, .actions button, .structure-actions a, .structure-actions button { margin-left: 9px; padding: 0; color: var(--forest-2); background: none; border: 0; font-size: 11px; font-weight: 700; cursor: pointer; }
.actions .danger-link, .structure-actions .danger-link { color: var(--red); }
.form-card-wide { max-width: 980px; padding: 30px; }
.admin-form { display: grid; gap: 26px; }
.form-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 20px; }
.form-grid.one-wide { grid-template-columns: 1fr; }
.check-row { display: flex; flex-wrap: wrap; gap: 22px; }
.admin-form label.check { display: flex; align-items: flex-start; grid-template-columns: auto 1fr; gap: 9px; font-weight: 600; cursor: pointer; }
.admin-form label.check input { width: 16px; min-height: 16px; margin-top: 2px; accent-color: var(--forest); }
.check span { display: grid; gap: 2px; }
.check small { display: block; }
.form-actions { padding-top: 20px; display: flex; justify-content: flex-end; gap: 10px; border-top: 1px solid var(--line); }
.structure-list { display: grid; gap: 18px; }
.structure-card { overflow: hidden; }
.structure-card > header { padding: 18px 20px; display: grid; grid-template-columns: 42px 1fr auto; align-items: center; gap: 13px; background: #f5f5f0; border-bottom: 1px solid var(--line); }
.structure-number { display: grid; width: 38px; height: 38px; place-items: center; color: white; background: var(--forest); border-radius: 10px; }
.structure-card h2, .structure-card p { margin: 0; }
.structure-card h2 { font-size: 15px; }
.structure-card p { color: #808983; font-size: 10px; }
.structure-lesson { min-width: 780px; padding: 13px 18px; display: grid; grid-template-columns: 20px 30px minmax(200px, 1fr) 70px 60px 100px; align-items: center; gap: 10px; border-bottom: 1px solid #ecece7; font-size: 11px; }
.structure-lesson:last-child { border-bottom: 0; }
.structure-lesson > div:nth-child(3) { display: grid; gap: 2px; }
.structure-lesson small { max-width: 460px; overflow: hidden; color: #89918c; font-size: 9px; text-overflow: ellipsis; white-space: nowrap; }
.drag-handle { color: #adb4af; letter-spacing: -4px; }
.lesson-index { color: #89918c; }
.structure-lessons { overflow-x: auto; }
.admin-empty { margin-top: 20px; }
.source-fieldset { margin: 0; padding: 0; border: 0; }
.source-fieldset legend { margin-bottom: 10px; font-size: 14px; font-weight: 700; }
.source-options { display: grid; grid-template-columns: repeat(2, 1fr); gap: 13px; }
.admin-form label.source-option { display: grid; padding: 16px; grid-template-columns: 20px 1fr; gap: 9px; background: #f7f8f4; border: 1px solid var(--line); border-radius: 12px; cursor: pointer; }
.source-option input { width: 16px; min-height: 16px; accent-color: var(--forest); }
.source-option span { display: grid; gap: 3px; }
.settings-section { display: grid; gap: 18px; padding-bottom: 27px; border-bottom: 1px solid var(--line); }
.settings-section h2 { margin: 0; font-size: 17px; }
.access-picker { display: grid; gap: 16px; padding: 22px; background: #f5f8fe; border: 1px solid var(--line); border-radius: 14px; }
.access-picker h2, .access-picker p { margin: 0; }
.access-picker h2 { font-size: 17px; }
.access-picker p { margin-top: 3px; color: #737e91; font-size: 12px; }
.access-user-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 10px; }
.admin-form label.access-user { padding: 11px; display: grid; grid-template-columns: 18px 34px minmax(0, 1fr); align-items: center; gap: 9px; background: white; border: 1px solid var(--line); border-radius: 10px; cursor: pointer; }
.admin-form label.access-user:has(input:checked) { background: #edf4ff; border-color: #8bb7f7; }
.access-user input { width: 15px; min-height: 15px; accent-color: var(--forest-2); }
.access-user > span:last-child { min-width: 0; display: grid; gap: 1px; }
.access-user strong, .access-user small { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.table-progress { min-width: 120px; display: grid; gap: 5px; }

@media (max-width: 1050px) {
  .course-grid { grid-template-columns: repeat(2, 1fr); }
  .stat-grid { grid-template-columns: repeat(2, 1fr); }
  .player-layout { grid-template-columns: 1fr 300px; }
  .admin-layout { grid-template-columns: 190px 1fr; }
}

@media (max-width: 800px) {
  .site-header { height: auto; min-height: 64px; padding: 12px 18px; align-items: flex-start; gap: 15px; }
  .top-nav { justify-content: flex-end; flex-wrap: wrap; gap: 12px; }
  .user-chip { display: none; }
  .login-shell { grid-template-columns: 1fr; }
  .login-intro { min-height: 300px; padding: 30px; }
  .intro-copy { margin-block: 55px 35px; }
  .intro-copy h1 { font-size: 48px; }
  .intro-security { display: none; }
  .login-panel { min-height: calc(100vh - 300px); padding: 30px 20px; }
  .course-hero-inner { grid-template-columns: 1fr; }
  .course-hero-art { display: none; }
  .player-layout { height: auto; min-height: calc(100vh - 72px); grid-template-columns: 1fr; }
  .video-column { padding: 22px 16px; }
  .video-stage { max-height: none; }
  .outline-panel { max-height: 500px; border-left: 0; border-top: 1px solid rgba(255,255,255,.1); }
  .outline-scroll { height: 430px; }
  .admin-layout { grid-template-columns: 1fr; }
  .admin-sidebar { position: static; height: auto; padding: 12px; }
  .admin-sidebar nav { grid-template-columns: repeat(4, 1fr); }
  .admin-sidebar nav a { justify-content: center; }
  .admin-label { display: none; }
  .admin-main { padding: 30px 18px 60px; }
}

@media (max-width: 620px) {
  .page-container { width: min(100% - 30px, 1180px); }
  .brand > span:last-child { display: none; }
  .top-nav { font-size: 12px; }
  .top-nav a:first-child { display: none; }
  .welcome-row, .admin-heading { align-items: flex-start; flex-direction: column; }
  .course-grid { grid-template-columns: 1fr; }
  .course-hero-inner { min-height: 380px; padding-block: 45px; }
  .back-link { margin-bottom: 28px; }
  .hero-stats { flex-wrap: wrap; gap: 14px 22px; }
  .lesson-row { padding-inline: 15px; grid-template-columns: 34px 1fr auto; }
  .lesson-duration { display: none; }
  .player-heading { align-items: flex-start; }
  .access-user-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .login-card { padding: 30px 24px; }
  .form-grid, .source-options { grid-template-columns: 1fr; }
  .stat-grid { grid-template-columns: 1fr 1fr; gap: 10px; }
  .stat-grid article { padding: 16px; }
  .admin-sidebar nav { grid-template-columns: repeat(2, 1fr); }
  .admin-sidebar nav a { justify-content: flex-start; }
  .notice { align-items: flex-start; flex-direction: column; }
  .structure-card > header { grid-template-columns: 36px 1fr; }
  .structure-actions { grid-column: 1 / -1; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; }
  .moving-watermark { animation-duration: 52s !important; animation-iteration-count: infinite !important; }
}

@media (max-width: 520px) {
  .site-header { position: static; padding: 10px 12px; }
  .top-nav { width: calc(100% - 46px); overflow-x: auto; justify-content: flex-start; flex-wrap: nowrap; white-space: nowrap; scrollbar-width: none; }
  .top-nav::-webkit-scrollbar { display: none; }
  .library-page { padding-block: 38px 60px; }
  .welcome-row { margin-bottom: 28px; }
  .welcome-row h1 { font-size: 29px; }
  .course-card-body { padding: 20px; }
  .course-hero-inner { min-height: 320px; padding-block: 35px; }
  .course-hero h1 { font-size: 35px; }
  .hero-stats { display: grid; grid-template-columns: 1fr 1fr; }
  .syllabus-section { padding-block: 42px 65px; }
  .chapter-header { padding: 17px 15px; }
  .lesson-row { min-height: 70px; }
  .player-layout { min-height: auto; }
  .video-column { padding: 16px 0 20px; }
  .player-heading { padding: 0 15px; }
  .player-heading h1 { font-size: 21px; }
  .video-stage { border-left: 0; border-right: 0; border-radius: 0; }
  .player-toolbar { padding: 0 12px; }
  .outline-panel { max-height: none; }
  .outline-scroll { height: auto; max-height: 460px; }
  .admin-main { padding-inline: 12px; }
  .admin-heading h1 { font-size: 30px; }
  .form-card-wide { padding: 20px 15px; }
  .access-user-grid { grid-template-columns: 1fr; }
  .stat-grid { grid-template-columns: 1fr; }
}

/* 轻量蓝色主题与播放器体验 */
.site-header { background: rgba(255,255,255,.95); border-bottom-color: #e5edf8; }
.brand-mark { color: white; background: linear-gradient(145deg, #78b2fa, #3b82f6); }
.top-nav > a { color: #627089; }
.muted { color: #748198; }
.stack-form input, .admin-form input, .admin-form textarea, .admin-form select { background: #fbfdff; border-color: #dbe5f2; }
.stack-form input:focus, .admin-form input:focus, .admin-form textarea:focus, .admin-form select:focus { border-color: #75aaf3; box-shadow: 0 0 0 4px rgba(91,156,245,.13); }

.login-intro { color: var(--ink); background: linear-gradient(145deg, #e9f3ff 0%, #f7fbff 68%, #dfeeff 100%); }
.login-intro::before, .login-intro::after { border-color: rgba(59,130,246,.12); }
.login-intro::before { box-shadow: 0 0 0 80px rgba(91,156,245,.04), 0 0 0 160px rgba(91,156,245,.025); }
.intro-copy p { color: #6b7a92; }
.login-panel { background: #f9fbff; }
.login-card { border-color: #e4ecf6; }

.course-card { border-color: #e4ebf5; box-shadow: 0 10px 40px rgba(61,103,164,.055); }
.course-card-locked { position: relative; background: #f0f3f8; border-color: #dce3ec; }
.course-card-locked:hover { transform: translateY(-3px); }
.course-card-locked .course-cover img,
.course-card-locked .cover-placeholder { filter: grayscale(.82); opacity: .55; }
.course-card-locked .course-card-body { color: #79859a; }
.course-card-locked h2 { color: #6c788c; }
.locked-badge { position: absolute; top: 14px; right: 14px; z-index: 3; padding: 7px 11px; color: #445168; background: rgba(255,255,255,.9); border: 1px solid rgba(112,127,151,.18); border-radius: 999px; box-shadow: 0 5px 18px rgba(47,61,82,.12); font-size: 12px; font-weight: 800; }
.locked-contact { color: #68758a; font-weight: 700; }
.circle-link.locked-link { color: #6f7b8d; background: #dce2eb; }

.course-hero { background: linear-gradient(135deg, #65a6f6, #3b82f6); }
.course-hero-art { background: linear-gradient(145deg, rgba(219,234,254,.35), rgba(255,255,255,.12)); }
.chapter-header { background: #f4f8fe; }
.chapter-number, .structure-number { background: var(--forest-2); }
.play-dot { color: #2775e7; background: #e7f1ff; }

.locked-page { width: min(1120px,calc(100% - 48px)); margin: 0 auto; padding-block: 64px 90px; }
.locked-course-card { overflow: hidden; display: grid; grid-template-columns: minmax(300px,.82fr) minmax(360px,1fr); background: white; border: 1px solid #e0e7f0; border-radius: 24px; box-shadow: var(--shadow); }
.locked-course-cover { position: relative; min-height: 430px; overflow: hidden; display: grid; place-items: center; background: #e5e9ef; }
.locked-course-cover img { width: 100%; height: 100%; object-fit: cover; filter: grayscale(1); opacity: .48; }
.locked-course-cover .cover-placeholder { position: absolute; inset: 0; filter: grayscale(1); opacity: .65; }
.locked-course-cover > span { position: absolute; z-index: 2; display: grid; width: 76px; height: 76px; place-items: center; background: rgba(255,255,255,.9); border-radius: 22px; box-shadow: 0 12px 35px rgba(41,53,71,.16); font-size: 34px; }
.locked-course-copy { padding: clamp(34px,5vw,72px); display: flex; justify-content: center; flex-direction: column; }
.locked-course-copy h1 { margin: 10px 0 13px; font-size: clamp(32px,4vw,48px); line-height: 1.2; }
.locked-course-copy > p { margin: 0; color: var(--ink-soft); }
.lock-circle { display: grid; width: 52px; height: 52px; place-items: center; color: #4e5c71; background: #edf1f6; border-radius: 15px; font-size: 23px; }
.unlock-callout { margin: 28px 0; padding: 19px 21px; display: grid; gap: 4px; color: #315f9f; background: #edf5ff; border: 1px solid #d2e5fd; border-radius: 14px; font-weight: 750; }
.unlock-callout span { color: #6381a9; font-size: 13px; font-weight: 600; }

.admin-page { background: #f6f9fd; }
.admin-sidebar { color: var(--ink); background: white; border-right: 1px solid #e0e8f3; }
.admin-label { color: #8a97aa; }
.admin-sidebar nav a { color: #64728a; }
.admin-sidebar nav a span { color: #4c91ef; }
.admin-sidebar nav a:hover, .admin-sidebar nav a.active { color: #246fda; background: #eaf3ff; }
.admin-card { box-shadow: 0 8px 30px rgba(47,88,146,.045); }
th { background: #f4f8fd; }
tbody tr:hover { background: #f7faff; }
.avatar { color: #2e78dd; background: #e6f1ff; }
.actions, .structure-actions { display: inline-flex; align-items: center; justify-content: flex-end; gap: 7px; }
.actions a, .actions button, .structure-actions a, .structure-actions button { min-height: 38px; margin-left: 0; padding: 8px 11px; display: inline-flex; align-items: center; gap: 6px; color: #2d78dc; background: #edf5ff; border: 1px solid #d9e9fc; border-radius: 9px; font-size: 12px; }
.actions a:hover, .actions button:hover, .structure-actions a:hover, .structure-actions button:hover { background: #dfeeff; }
.actions .danger-link, .structure-actions .danger-link { color: #b43c3c; background: #fff1f1; border-color: #f4d7d7; }
.access-user-list { display: grid; grid-template-columns: 1fr; gap: 9px; }
.admin-form label.access-user { padding: 12px 14px; grid-template-columns: 38px minmax(0,1fr) 24px; gap: 12px; border-radius: 11px; }
.admin-form label.access-user:has(input:checked) { background: #eef6ff; border-color: #9cc4f8; }
.access-user input { width: 18px; height: 18px; min-height: 18px; grid-column: 3; grid-row: 1; justify-self: center; }
.access-user .avatar { grid-column: 1; grid-row: 1; }
.access-user > span:last-child { grid-column: 2; grid-row: 1; }
.detected-duration { display: inline-flex; min-height: 40px; padding: 9px 12px; align-items: center; color: #4b6385; background: #f2f7fd; border: 1px solid #dfe9f5; border-radius: 9px; font-size: 12px; }

/* 播放器默认白色，用户可在页头切换黑色并记住选择 */
body.player-page { --player-bg: #f4f7fb; --player-panel: #ffffff; --player-panel-soft: #f7f9fc; --player-text: #26344d; --player-muted: #758298; --player-line: #dfe7f1; background: var(--player-bg); }
body.player-page[data-player-theme="dark"] { color-scheme: dark; --player-bg: #0d1422; --player-panel: #141e30; --player-panel-soft: #19263b; --player-text: #f1f5fb; --player-muted: #9ba8bb; --player-line: rgba(255,255,255,.1); }
.player-page .site-header { color: var(--player-text); background: color-mix(in srgb, var(--player-panel) 96%, transparent); border-color: var(--player-line); }
.player-page .brand-mark { color: white; background: #4f93ed; }
.player-page .top-nav > a, .player-page .nav-button { color: var(--player-muted); }
.player-page .user-chip { color: var(--player-text); background: var(--player-panel-soft); border-color: var(--player-line); }
.player-layout { width: min(1500px,100%); height: auto; min-height: calc(100vh - 72px); margin: 0 auto; padding: 24px; display: grid; grid-template-columns: minmax(0,1fr) 310px; align-items: start; gap: 18px; }
.video-column { min-width: 0; overflow: visible; padding: 0; }
.player-heading { min-height: 66px; margin-bottom: 16px; align-items: center; color: var(--player-text); }
.player-heading a, .player-heading p { color: var(--player-muted); }
.player-theme-switch { padding: 4px; display: inline-grid; grid-template-columns: 1fr 1fr; gap: 3px; background: var(--player-panel-soft); border: 1px solid var(--player-line); border-radius: 13px; }
.player-theme-switch button { min-width: 82px; min-height: 42px; padding: 8px 12px; color: var(--player-muted); background: transparent; border: 0; border-radius: 9px; font-weight: 700; cursor: pointer; }
.player-theme-switch button.active { color: #246fda; background: var(--player-panel); box-shadow: 0 3px 12px rgba(33,63,106,.12); }
body.player-page[data-player-theme="dark"] .player-theme-switch button.active { color: white; background: #273750; }
.video-stage { max-height: none; background: #02050a; border-color: rgba(110,133,168,.28); border-radius: 14px; box-shadow: 0 18px 52px rgba(26,50,86,.16); }
.custom-video-controls { position: absolute; left: 0; right: 0; bottom: 0; z-index: 7; min-height: 76px; padding: 25px 16px 12px; display: grid; grid-template-columns: 46px minmax(100px,1fr) auto 46px 90px 72px 46px; align-items: center; gap: 10px; color: white; background: linear-gradient(transparent,rgba(0,0,0,.88)); opacity: 1; transition: opacity .2s; }
.video-control-button { width: 44px; height: 44px; display: grid; place-items: center; color: white; background: rgba(255,255,255,.12); border: 1px solid rgba(255,255,255,.2); border-radius: 12px; cursor: pointer; font-size: 17px; }
.video-control-button:hover { background: rgba(255,255,255,.22); }
.seek-control { min-width: 0; display: flex; align-items: center; }
.seek-control input, .volume-slider { width: 100%; height: 20px; margin: 0; accent-color: #64a5fa; cursor: pointer; }
.video-time { min-width: 98px; font-size: 11px; text-align: center; white-space: nowrap; }
.speed-select { width: 72px; height: 42px; padding: 0 8px; color: white; background: rgba(20,25,35,.72); border: 1px solid rgba(255,255,255,.2); border-radius: 10px; cursor: pointer; }
.player-message { z-index: 8; }
.player-toolbar { margin-top: 14px; }
.player-toolbar a { color: var(--player-text); background: var(--player-panel); border-color: var(--player-line); }
.player-toolbar a:hover { background: var(--player-panel-soft); border-color: #a7c9f7; }
.player-toolbar small { color: var(--player-muted); }
.outline-panel { max-height: calc(100vh - 120px); overflow: hidden; color: var(--player-text); background: var(--player-panel); border: 1px solid var(--player-line); border-radius: 14px; box-shadow: 0 10px 36px rgba(35,66,109,.08); }
.outline-title { height: 64px; border-color: var(--player-line); }
.outline-title strong { color: var(--player-muted); }
.outline-scroll { height: auto; max-height: calc(100vh - 184px); padding-bottom: 14px; }
.outline-chapter { color: var(--player-muted); }
.outline-lesson { color: var(--player-muted); }
.outline-lesson:hover { background: var(--player-panel-soft); }
.outline-lesson.active { color: var(--player-text); background: #e9f3ff; }
body.player-page[data-player-theme="dark"] .outline-lesson.active { background: rgba(91,156,245,.18); }
.outline-play { color: #4d94ee; }
.outline-lesson small { color: var(--player-muted); }
.video-stage:fullscreen { width: 100vw; height: 100vh; aspect-ratio: auto; border: 0; border-radius: 0; }
.video-stage:fullscreen video { width: 100%; height: 100%; }

@media (max-width: 1050px) {
  .player-layout { grid-template-columns: minmax(0,1fr) 280px; }
  .custom-video-controls { grid-template-columns: 46px minmax(80px,1fr) auto 46px 72px 46px; }
  .volume-slider { display: none; }
}

@media (max-width: 800px) {
  .locked-course-card { grid-template-columns: 1fr; }
  .locked-course-cover { min-height: 290px; }
  .player-layout { min-height: auto; padding: 18px 14px 30px; grid-template-columns: 1fr; }
  .outline-panel { max-height: none; border: 1px solid var(--player-line); }
  .outline-scroll { height: auto; max-height: 430px; }
  .admin-sidebar { border-right: 0; border-bottom: 1px solid #e0e8f3; }
}

@media (max-width: 620px) {
  .player-heading { min-height: 0; align-items: stretch; flex-direction: column; gap: 14px; }
  .player-theme-switch { align-self: flex-start; }
  .custom-video-controls { min-height: 64px; padding: 22px 8px 8px; grid-template-columns: 42px minmax(60px,1fr) auto 42px 56px 42px; gap: 5px; }
  .video-control-button { width: 40px; height: 40px; border-radius: 10px; }
  .volume-slider { display: none; }
  .speed-select { width: 56px; height: 40px; padding-inline: 4px; font-size: 11px; }
  .video-time { min-width: 76px; font-size: 9px; }
}

@media (max-width: 520px) {
  .locked-page { padding-block: 32px 55px; }
  .locked-course-cover { min-height: 220px; }
  .locked-course-copy { padding: 28px 22px; }
  .player-layout { padding: 14px 0 28px; }
  .player-heading { padding-inline: 14px; }
  .player-theme-switch { width: 100%; }
  .player-theme-switch button { min-width: 0; }
  .player-toolbar { padding-inline: 10px; }
  .outline-panel { margin-inline: 10px; border-radius: 12px; }
  .video-stage { width: 100%; min-width: 0; }
  .custom-video-controls { width: 100%; min-width: 0; overflow: hidden; padding-inline: 6px; display: grid; grid-template-columns: 36px minmax(0,1fr) 36px 52px 36px; gap: 4px; }
  .custom-video-controls .seek-control,
  .custom-video-controls .seek-control input { width: 100%; min-width: 0; }
  .custom-video-controls .video-control-button { width: 36px; min-width: 0; height: 40px; }
  .video-time, .volume-slider { display: none; }
  .speed-select { width: 52px; min-width: 0; max-width: 52px; padding-inline: 3px; color: white; font-size: 11px; }
  .speed-select option { color: white; font-size: 12px; }
}

/* 手机端直接展示登录表单，并压缩登录后的顶部导航 */
@media (max-width: 800px) {
  .login-shell { min-height: 100svh; display: block; background: #f6f9fe; }
  .login-intro { display: none; }
  .login-panel { min-height: 100svh; padding: 20px; justify-content: center; background: #f6f9fe; }
  .login-card { width: min(430px,100%); }
}

@media (max-width: 620px) {
  .site-header { min-height: 64px; padding: 10px 14px; align-items: center; gap: 10px; }
  .brand { min-width: 0; flex: 0 1 auto; gap: 8px; font-size: 13px; }
  .brand > span:last-child { max-width: 118px; display: inline; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .brand-mark { flex: 0 0 36px; width: 36px; height: 36px; border-radius: 10px; }
  .top-nav { width: auto; min-width: 0; margin-left: auto; justify-content: flex-end; flex: 1 1 auto; gap: 11px; overflow: visible; font-size: 12px; }
  .top-nav a, .top-nav button { flex: 0 0 auto; }
}

@media (max-width: 520px) {
  .site-header { position: sticky; top: 0; }
  .login-panel { padding: 16px; }
  .login-card { padding: 30px 24px; border-radius: 22px; }
  .login-card h2 { font-size: 29px; }
  .stack-form { margin-top: 24px; }
}

.stack-form label.remember-login { margin-top: -4px; display: flex; align-items: center; gap: 9px; color: #63728a; font-size: 13px; font-weight: 600; cursor: pointer; }
.stack-form label.remember-login input { width: 18px; height: 18px; margin: 0; accent-color: var(--forest-2); }

.course-hero .back-link { min-height: 46px; margin-bottom: 28px; padding: 0 15px; display: inline-flex; align-items: center; color: white; background: rgba(255,255,255,.16); border: 1px solid rgba(255,255,255,.3); border-radius: 12px; font-size: 14px; font-weight: 750; box-shadow: 0 8px 24px rgba(34,91,174,.12); }
.course-hero .back-link:hover { background: rgba(255,255,255,.24); }
.hero-stats span { min-width: 0; }

@media (max-width: 620px) {
  .course-hero-inner { min-height: auto; padding-block: 22px 26px; display: block; }
  .course-hero .back-link { min-height: 48px; margin-bottom: 20px; padding-inline: 16px; font-size: 14px; }
  .course-hero h1 { margin: 0 0 8px; font-size: 34px; line-height: 1.15; }
  .course-hero-copy > p { max-width: none; font-size: 14px; }
  .hero-stats { margin-top: 20px; display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 10px; }
  .hero-stats span { padding: 12px 14px; display: flex; align-items: baseline; gap: 6px; background: rgba(255,255,255,.13); border: 1px solid rgba(255,255,255,.18); border-radius: 12px; }
  .hero-stats strong { margin: 0; font-size: 20px; }
  .syllabus-section { padding-block: 30px 56px; }
  .section-heading { margin-bottom: 18px; }
  .section-heading h2 { font-size: 30px; }
  .syllabus-list { gap: 14px; }
  .chapter-block { border-radius: 15px; }
  .chapter-header { padding: 16px; }
  .chapter-number { width: 40px; height: 40px; }
}

@media (max-width: 520px) {
  .course-hero-inner { padding-block: 18px 22px; }
  .course-hero .back-link { width: 100%; margin-bottom: 18px; justify-content: center; }
  .course-hero h1 { font-size: 32px; }
  .hero-stats { margin-top: 18px; }
  .syllabus-section { padding-block: 26px 48px; }
  .section-heading h2 { font-size: 28px; }
}

/* 后台管理视觉与统一返回操作 */
.admin-page { background: #f3f7fc; }
.admin-layout { grid-template-columns: 244px minmax(0,1fr); }
.admin-sidebar { padding: 30px 18px; color: #2d405f; background: linear-gradient(180deg,#edf5ff 0%,#f8fbff 100%); border-right: 1px solid #d8e6f7; }
.admin-label { padding-inline: 14px; color: #7c91ad; font-size: 11px; letter-spacing: .12em; }
.admin-sidebar nav { gap: 8px; }
.admin-sidebar nav a { min-height: 46px; padding: 11px 14px; color: #5b6e89; border: 1px solid transparent; border-radius: 12px; font-size: 14px; font-weight: 650; }
.admin-sidebar nav a span { color: #458bec; font-size: 16px; }
.admin-sidebar nav a:hover { color: #246fda; background: rgba(255,255,255,.78); border-color: #d7e6f8; }
.admin-sidebar nav a.active { color: white; background: linear-gradient(135deg,#67a7f7,#3b82f6); border-color: transparent; box-shadow: 0 9px 24px rgba(59,130,246,.2); }
.admin-sidebar nav a.active span { color: white; }
.admin-main { padding-top: 38px; }
.admin-heading { margin-bottom: 24px; align-items: center; }
.admin-heading h1 { margin-top: 10px; color: #22334e; }
.admin-heading p { color: #71819a; }
.admin-card { border-color: #dfe9f5; border-radius: 20px; box-shadow: 0 12px 38px rgba(41,84,145,.065); }
.form-card-wide { max-width: 1040px; }
.card-heading { background: linear-gradient(180deg,#fff,#fbfdff); }
th { color: #6f8099; background: #f1f6fc; }
td { border-top-color: #e7eef7; }
tbody tr:hover { background: #f6faff; }

.back-link.dark-link { min-height: 44px; margin: 0; padding: 0 14px; display: inline-flex; align-items: center; color: #2f76d3; background: white; border: 1px solid #d8e7f8; border-radius: 11px; box-shadow: 0 6px 18px rgba(48,100,170,.08); font-size: 13px; font-weight: 750; }
.back-link.dark-link:hover { color: #1f65c5; background: #edf5ff; border-color: #bcd7f8; }

.access-picker { gap: 18px; padding: 24px; background: linear-gradient(180deg,#f7fbff,#f1f7fe); border-color: #d9e7f7; border-radius: 16px; }
.access-picker-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 18px; }
.access-picker-head > strong { min-height: 34px; padding: 7px 11px; display: inline-flex; align-items: center; color: #2f75d0; background: white; border: 1px solid #d8e8fa; border-radius: 999px; font-size: 12px; white-space: nowrap; }
.access-tools { display: grid; grid-template-columns: minmax(220px,1fr) auto; gap: 10px; }
.admin-form label.access-search { position: relative; display: flex; align-items: center; gap: 0; font-weight: 500; }
.access-search > span { position: absolute; left: 14px; z-index: 1; color: #6f87a8; font-size: 20px; pointer-events: none; }
.admin-form .access-search input { min-height: 48px; padding-left: 43px; background: white; border-color: #d6e4f5; }
.access-select-button { min-width: 112px; min-height: 48px; color: #276ecb; background: white; border-color: #cfe1f7; }
.access-select-button:hover { background: #e7f2ff; border-color: #a9caf3; }
.access-select-button:disabled { color: #9ca9bb; background: #f1f4f8; cursor: not-allowed; transform: none; }
.access-user-list { max-height: 430px; overflow-y: auto; padding-right: 4px; scrollbar-width: thin; }
.admin-form label.access-user { min-height: 62px; padding: 11px 14px; border-color: #dfe8f3; box-shadow: 0 3px 12px rgba(45,84,137,.035); }
.admin-form label.access-user:hover { border-color: #b8d2f3; background: #fbfdff; }
.admin-form label.access-user:has(input:checked) { background: #e7f2ff; border-color: #82b1ef; box-shadow: inset 3px 0 #438cf0; }
.access-no-results { padding: 30px 18px; color: #7a889d; text-align: center; background: rgba(255,255,255,.65); border: 1px dashed #cbd9e9; border-radius: 12px; }

@media (max-width: 1050px) {
  .admin-layout { grid-template-columns: 210px minmax(0,1fr); }
}

@media (max-width: 800px) {
  .admin-layout { grid-template-columns: 1fr; }
  .admin-sidebar { position: sticky; top: 64px; z-index: 30; height: auto; padding: 9px 12px; overflow-x: auto; border-right: 0; border-bottom: 1px solid #d9e6f5; scrollbar-width: none; }
  .admin-sidebar::-webkit-scrollbar { display: none; }
  .admin-sidebar nav { width: max-content; display: flex; gap: 7px; }
  .admin-sidebar nav a { min-height: 42px; padding: 9px 12px; white-space: nowrap; }
  .admin-main { padding: 28px 16px 58px; }
}

@media (max-width: 620px) {
  .admin-heading { gap: 16px; }
  .admin-heading h1 { margin-top: 8px; font-size: 30px; }
  .back-link.dark-link { min-height: 46px; padding-inline: 15px; }
  .access-picker { padding: 18px 14px; }
  .access-picker-head { align-items: flex-start; }
  .access-tools { grid-template-columns: 1fr; }
  .access-select-button { width: 100%; }
}

@media (max-width: 520px) {
  .admin-sidebar { top: 64px; }
  .admin-main { padding: 24px 12px 48px; }
  .admin-card { border-radius: 16px; }
  .form-card-wide { padding: 19px 14px; }
  .back-link.dark-link { width: 100%; justify-content: center; }
  .access-picker-head { flex-direction: column; gap: 10px; }
}

/* 表格操作列贴边、目录配色与手机登录品牌 */
.login-mobile-brand { display: none; }
th.align-right:last-child,
td.actions.align-right { width: 1%; white-space: nowrap; }
td.actions { display: table-cell; text-align: right; }
td.actions > a,
td.actions > form { margin-left: 7px; vertical-align: middle; }
.structure-card > header { background: linear-gradient(90deg,#eef6ff 0%,#f8fbff 58%,#ffffff 100%); border-bottom-color: #d8e6f5; }
.structure-card > header h2 { color: #273b59; }
.structure-card > header p { color: #71839d; }
.structure-lessons { background: white; }

@media (max-width: 800px) {
  .login-panel { position: relative; padding-top: 76px; }
  .login-mobile-brand { position: absolute; top: 20px; left: 20px; display: inline-flex; align-items: center; gap: 10px; color: #243754; font-size: 15px; font-weight: 800; }
  .login-mobile-brand .brand-mark { width: 38px; height: 38px; flex: 0 0 38px; }
}

@media (max-width: 520px) {
  .login-panel { padding: 76px 16px 16px; }
  .login-mobile-brand { top: 18px; left: 18px; }
}

/* 手机播放器紧凑布局 */
.player-heading-main { min-width: 0; display: flex; align-items: center; gap: 14px; }
.player-heading-copy { min-width: 0; }
.player-back-button { min-width: 84px; min-height: 48px; padding: 0 14px; display: inline-flex; align-items: center; justify-content: center; gap: 7px; color: white !important; background: #3b82f6; border: 1px solid #3b82f6; border-radius: 12px; box-shadow: 0 7px 18px rgba(59,130,246,.2); font-size: 13px !important; font-weight: 750; }
.player-back-button:hover { background: #2f76df; border-color: #2f76df; }
.player-back-button span:first-child { font-size: 18px; line-height: 1; }
.player-heading-copy h1 { margin: 0 0 2px; }
.player-heading-copy p { margin: 0; }
.player-toolbar.single-lesson-nav { grid-template-columns: 1fr; }

@media (max-width: 620px) {
  .player-layout { padding: 12px 0 22px; gap: 10px; }
  .video-column { padding: 0; }
  .player-heading { margin-bottom: 10px; padding-inline: 12px; flex-direction: row; align-items: center; gap: 8px; }
  .player-heading-main { width: auto; flex: 1 1 auto; gap: 10px; }
  .player-back-button { min-width: 82px; min-height: 46px; padding-inline: 12px; }
  .player-heading-copy h1 { overflow: hidden; font-size: 22px; text-overflow: ellipsis; white-space: nowrap; }
  .player-heading-copy p { font-size: 12px; }
  .player-theme-switch { width: 148px; flex: 0 0 148px; align-self: center; padding: 2px; border-radius: 10px; }
  .player-theme-switch button { min-width: 0; min-height: 34px; padding: 4px 7px; border-radius: 8px; font-size: 12px; }
  .player-toolbar { margin-top: 9px; padding-inline: 10px; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 8px; }
  .player-toolbar.single-lesson-nav { grid-template-columns: 1fr; }
  .player-toolbar a { min-height: 50px; padding: 9px 13px; align-content: center; }
  .player-toolbar .next-lesson { text-align: right; }
  .outline-panel { margin: 0 10px; }
  .outline-title { height: 56px; padding-inline: 16px; }
  .outline-title span { font-size: 16px; }
}

@media (max-width: 520px) {
  .player-layout { padding-top: 10px; }
  .player-heading { padding-inline: 10px; }
  .player-back-button { min-width: 80px; }
  .player-theme-switch { width: 138px; flex-basis: 138px; }
  .player-toolbar { padding-inline: 10px; }
}

.training-search{display:flex;gap:12px;margin:0 0 28px;flex-wrap:wrap;align-items:center}.training-search input{flex:1;min-width:200px;padding:14px;border:1px solid #cbd5e1;border-radius:12px}.training-tags{display:flex;gap:8px;flex-wrap:wrap;font-size:12px;color:#496a8f;margin:10px 0}.material-row{display:flex;gap:16px;flex-wrap:wrap;align-items:center;padding:16px 0;border-bottom:1px solid #e2e8f0}.material-name{flex:1;overflow-wrap:anywhere}.preview-table{overflow:auto;margin:18px 0;max-height:600px}.preview-table table{border-collapse:collapse;width:100%}.preview-table td{border:1px solid #d7e0eb;padding:8px;white-space:pre-wrap}.document-content p{white-space:pre-wrap;overflow-wrap:anywhere}.pdf-preview{width:100%;height:78vh;border:1px solid #ccd6e0}.training-notice{padding:16px;background:#edf4fc;border-radius:12px}
/* Course authoring and resource workspace */
.padded-card,.editor-card{padding:28px;margin-bottom:22px}.padded-card .card-heading{padding:0 0 18px}.padded-card h2{margin:0;font-size:19px}.heading-actions{display:flex;gap:10px;flex-wrap:wrap;justify-content:flex-end}.materials-workspace{display:grid;grid-template-columns:240px minmax(0,1fr);gap:24px;align-items:start}.materials-scopes{background:#fff;border:1px solid #e2eaf5;border-radius:20px;padding:20px 12px;position:sticky;top:90px;max-height:80vh;overflow:auto}.materials-scopes h2{font-size:14px;color:#7b8fa8;padding:0 12px;margin:0 0 16px}.materials-scopes a{display:block;color:#425a76;padding:12px;border-radius:10px;overflow-wrap:anywhere;font-size:14px}.materials-scopes a.active{color:#2563eb;background:#edf4ff;font-weight:700}.materials-scopes .scope-lesson{padding-left:32px;font-size:13px}.materials-scopes>small{display:block;color:#7b8fa8;margin:16px 12px 4px}.materials-main{min-width:0}.scope-badge{display:inline-flex;align-items:center;padding:8px 14px;border:1px solid #dbeafe;background:#eff6ff;color:#2563eb;font-size:13px;border-radius:30px;white-space:nowrap}.file-dropzone{display:flex!important;flex-direction:column;gap:10px;align-items:center;justify-content:center;text-align:center;min-height:180px;background:#f8fbff;border:2px dashed #c9daf4;border-radius:16px;cursor:pointer;transition:background .2s,border-color .2s;padding:24px!important}.file-dropzone:hover,.file-dropzone.drag-over,.cover-dropzone.drag-over{background:#eff6ff;border-color:#3b82f6}.file-input-hidden{position:absolute!important;width:1px!important;height:1px!important;overflow:hidden!important;clip-path:inset(50%);padding:0!important;border:0!important}.file-dropzone:focus-within,.cover-dropzone:focus-within{outline:3px solid #93c5fd;outline-offset:3px}.upload-icon{display:flex;align-items:center;justify-content:center;width:48px;height:48px;border-radius:14px;background:#e6efff;color:#3b82f6;font-size:28px}.file-dropzone strong{font-size:15px}.file-dropzone small{color:#8294ad;font-size:12px}.upload-block>p{font-size:13px;color:#71839b;margin:10px 0 0;overflow-wrap:anywhere}.upload-actions{display:flex;align-items:center;justify-content:space-between;gap:16px}.upload-actions>span{font-size:12px;color:#8a9ab0}.upload-actions .button{width:auto!important;padding:12px 26px!important}.material-row{padding:18px 0;gap:14px}.material-name strong{display:block;font-size:14px;color:#223c5b}.material-name small{display:block;color:#93a1b4;font-size:12px;margin-top:5px}.material-file-icon{min-width:44px;height:48px;padding:0 6px;display:flex;align-items:center;justify-content:center;border-radius:10px;background:#edf3ff;color:#4776c5;font-weight:800;font-size:10px}.resource-link{font-size:13px;color:#3478ee}.resource-empty{text-align:center;padding:34px 20px;color:#899bb2}.resource-empty>span{font-size:32px;color:#b8cae2}.resource-empty p{font-size:14px;margin:8px 0}.resource-empty small{font-size:12px}.job-row{display:flex;gap:14px;align-items:center;padding:18px 0;border-bottom:1px solid #edf1f7}.job-row>div{flex:1}.job-row strong{font-size:14px}.job-row small{display:block;color:#d37853;font-size:12px;margin-top:6px}.job-icon{font-size:12px;color:#5c8dec;padding:12px;background:#f0f5ff;border-radius:10px}.job-row .status{font-size:12px}.cover-field{display:flex;flex-direction:column;gap:10px}.field-label{font-weight:700;font-size:14px}.cover-dropzone{height:210px;position:relative;display:flex!important;align-items:center;justify-content:center;border:2px dashed #c9daf4;border-radius:16px;background:#f5f9ff;overflow:hidden;cursor:pointer}.cover-dropzone img{width:100%;height:100%;object-fit:cover;position:absolute;inset:0}.cover-dropzone img:not([hidden])~.cover-placeholder-text{background:#142c4e99;color:white;padding:10px;opacity:0}.cover-dropzone:hover .cover-placeholder-text{opacity:1!important}.cover-placeholder-text{z-index:1;display:flex;flex-direction:column;align-items:center;gap:10px;text-align:center;transition:opacity .2s}.cover-placeholder-text>b{font-size:32px;color:#4e83d2}.cover-placeholder-text strong{font-size:14px}.cover-placeholder-text small{font-size:12px;color:#8196b3}.access-summary{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:22px;border:1px solid #e1eaf8;border-radius:16px;background:#f8fbff}.access-summary h2{font-size:16px;margin:0 0 7px}.access-summary p{font-size:12px;color:#8093ad;line-height:1.8;margin:0 0 10px}.access-summary strong{color:#3478ee;font-size:13px}.training-dialog{border:1px solid #dfe7f2;border-radius:22px;padding:0;width:min(820px,calc(100vw - 32px));max-height:85vh;color:#243c58;box-shadow:0 30px 100px #152d5040}.training-dialog::backdrop{background:#122b4d66;backdrop-filter:blur(3px)}.training-dialog>header{display:flex;align-items:flex-start;justify-content:space-between;padding:24px;border-bottom:1px solid #eaf0f8}.training-dialog h2{margin:0;font-size:21px}.training-dialog header p{margin:8px 0 0;color:#8a9ab0;font-size:13px;overflow-wrap:anywhere}.icon-button{border:none;background:#f2f6fc;color:#71859f;border-radius:10px;width:34px;height:34px;font-size:24px;cursor:pointer}.dialog-tools{display:flex;gap:10px;align-items:center;padding:18px 24px}.dialog-tools input{min-width:0;flex:1;border:1px solid #d8e4f4;border-radius:10px;padding:12px;font:inherit}.dialog-tools .button{font-size:12px;white-space:nowrap;padding:10px 13px}.training-dialog>p{padding:0 24px;font-size:12px;color:#8091a8}.modal-user-list{height:340px;overflow:auto;padding:0 24px}.modal-user-list .access-user{margin-bottom:8px;padding:12px;min-height:60px}.modal-user-list .access-user>span:nth-child(2){flex:1}.modal-user-list strong,.modal-user-list small{display:block}.modal-user-list small{font-size:12px;color:#8c9cb1;margin-top:4px}.training-dialog>footer{padding:18px 24px;display:flex;gap:10px;align-items:center;border-top:1px solid #eaf0f8;background:#fafcff;flex-wrap:wrap}.training-dialog footer>span:first-child{flex:1;color:#7c90ac;font-size:13px}.training-dialog footer .button{font-size:12px;padding:10px 16px}.initial-password{border:1px solid #e1eaf8;border-radius:12px;background:#f8fbff;padding:16px;display:flex;flex-direction:column;gap:8px}.initial-password strong{letter-spacing:3px;color:#285b9b}.initial-password small{color:#899db5;font-size:12px}.input-with-action{display:flex;gap:8px}.input-with-action input{min-width:0;flex:1}.input-with-action .button{white-space:nowrap;font-size:12px;padding:10px 14px}.advanced-settings{border:1px solid #e1eaf8;background:#fafcff;border-radius:14px;padding:18px;margin:10px 0}.advanced-settings summary{cursor:pointer;font-weight:700;color:#426387;font-size:14px}.advanced-settings p,.advanced-settings li{font-size:13px;line-height:1.9;color:#8192aa}.advanced-settings label{margin-top:12px}.video-file-list{height:340px;overflow:auto;padding:8px 24px}.video-file-row{display:flex;align-items:center;justify-content:space-between;gap:14px;width:100%;border:1px solid #e2eaf6;background:#fff;border-radius:12px;padding:16px;margin-bottom:10px;cursor:pointer;text-align:left;color:#36526f}.video-file-row:hover{background:#eff6ff;border-color:#a9c8f8}.video-file-row strong{font-size:13px;overflow-wrap:anywhere}.video-file-row small{white-space:nowrap;color:#8597ae;font-size:12px}.video-file-row.folder{color:#3a7de8;font-weight:700}.structure-lesson-copy{flex:1;min-width:0}.structure-lesson .actions{flex-wrap:wrap}.reading-card{background:#fff;border:1px solid #e2eaf6;border-radius:22px;padding:40px;margin-bottom:24px;max-width:960px}.article-layout{padding-top:32px;padding-bottom:48px;max-width:1040px}.reading-card header{border-bottom:1px solid #edf1f7;padding:24px 0;margin-bottom:28px}.reading-card h1{font-size:30px;margin:18px 0 10px}.reading-card header p{font-size:13px;color:#8b9ab0}.article-body{font-size:16px;line-height:2;color:#415672}.article-body p{white-space:pre-wrap;overflow-wrap:anywhere}.article-body img{display:block;max-width:100%;height:auto;border-radius:12px;margin:22px auto}.reading-card>form{margin-top:30px}.chapter-resources{padding:18px 24px;background:#f9fbff}.chapter-resources h4{margin:0;color:#677f9f;font-size:13px}.storage-status{display:flex;align-items:center;gap:14px;flex-wrap:wrap;margin:18px 0}.storage-status>span:last-child{font-size:13px;color:#6e87a4}.related-materials{margin-top:24px}.training-dialog [hidden],.admin-form [hidden],.cover-dropzone [hidden]{display:none!important}
@media(max-width:900px){.materials-workspace{grid-template-columns:1fr}.materials-scopes{position:static;max-height:240px}.admin-heading{flex-wrap:wrap}.heading-actions{justify-content:flex-start}.padded-card,.editor-card{padding:20px}.access-summary{flex-direction:column;align-items:flex-start}.structure-lesson{flex-wrap:wrap}.reading-card{padding:24px}}
@media(max-width:560px){.dialog-tools{flex-wrap:wrap}.dialog-tools input{flex-basis:100%}.training-dialog>footer{gap:7px}.training-dialog footer .button{padding:10px}.upload-actions{flex-direction:column;align-items:stretch}.material-row{gap:10px}.material-name{min-width:120px}.cover-dropzone{height:180px}}
.training-dialog[open]{display:flex;flex-direction:column;overflow:hidden}.training-dialog>header,.training-dialog>.dialog-tools,.training-dialog>footer,.training-dialog>p{flex-shrink:0}.modal-user-list,.video-file-list{flex:1 1 340px;min-height:100px;overflow:auto}