:root {
  --ink: #142b3a;
  --muted: #65808d;
  --line: #dbe6e9;
  --paper: #f7faf8;
  --white: #fffefd;
  --navy: #143850;
  --blue: #237aa5;
  --blue-pale: #e7f5f8;
  --gold: #e2a63e;
  --danger: #c65b4f;
  --shadow: 0 13px 34px rgba(20, 56, 80, .11);
  font-family: ui-rounded, "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  color: var(--ink);
  background: var(--paper);
}
* { box-sizing: border-box; }
body { margin: 0; min-width: 320px; background: var(--paper); }
button, input, textarea, select { font: inherit; }
button { cursor: pointer; }
button:disabled { opacity: .45; cursor: not-allowed; }
.login-shell { min-height: 100vh; display: grid; grid-template-columns: 1.05fr .95fr; background: #f4f8f6; }
.login-art { background: linear-gradient(150deg, #123c56 0%, #1f718c 55%, #8cc8c1 130%); padding: clamp(36px, 7vw, 100px); color: white; position: relative; overflow: hidden; }
.login-art::before, .login-art::after { content: ""; position: absolute; border: 1px solid rgba(255,255,255,.16); border-radius: 50%; }
.login-art::before { width: 540px; height: 540px; right: -230px; top: -150px; }
.login-art::after { width: 350px; height: 350px; left: -210px; bottom: -160px; }
.brand { display: flex; gap: 11px; align-items: center; font-weight: 700; letter-spacing: .04em; }
.brand-mark { width: 36px; height: 36px; display:grid; place-items:center; border:1px solid currentColor; border-radius: 10px; font-family: Georgia, serif; font-size: 21px; }
.login-art h1 { max-width: 590px; position: relative; z-index: 1; margin: clamp(90px, 16vh, 190px) 0 20px; font: 500 clamp(34px, 4.3vw, 66px)/1.14 Georgia, "Songti SC", serif; letter-spacing: .04em; }
.login-art p { position: relative; z-index: 1; max-width: 520px; line-height: 1.9; color: rgba(255,255,255,.82); }
.login-points { position: relative; z-index: 1; margin-top: 54px; padding: 0; list-style:none; display: grid; gap: 13px; font-size: 14px; color: #dbf4ef; }
.login-points li::before { content: "✦"; margin-right: 10px; color: #f7cb6b; }
.login-card-wrap { display: grid; place-items: center; padding: 36px; }
.login-card { width: min(390px, 100%); padding: 38px; background: var(--white); box-shadow: var(--shadow); border: 1px solid rgba(20,56,80,.06); border-radius: 18px; }
.eyebrow { color: var(--blue); font-weight: 700; font-size: 12px; letter-spacing: .14em; text-transform: uppercase; }
.login-card h2 { margin: 10px 0 8px; font: 600 30px Georgia, "Songti SC", serif; }
.subtle { color: var(--muted); font-size: 14px; line-height: 1.65; }
.field { display: grid; gap: 7px; margin-top: 18px; font-size: 13px; font-weight: 700; color: #48616f; }
.field input, .field textarea, .field select { width: 100%; border: 1px solid #cfdee2; border-radius: 9px; padding: 11px 12px; color: var(--ink); background: white; outline: none; transition: .15s; }
.field textarea { min-height: 76px; resize: vertical; line-height: 1.5; }
.field input:focus, .field textarea:focus, .field select:focus { border-color: var(--blue); box-shadow: 0 0 0 3px rgba(35,122,165,.12); }
.btn { border: 1px solid transparent; border-radius: 9px; min-height: 40px; padding: 0 14px; background: white; color: var(--ink); font-weight: 700; transition: transform .15s, background .15s; }
.btn:hover:not(:disabled) { transform: translateY(-1px); }
.btn-primary { background: var(--navy); color: white; }
.btn-blue { background: var(--blue); color: white; }
.btn-soft { background: var(--blue-pale); color: #176181; }
.btn-danger { color: var(--danger); border-color: #ebc9c5; background: #fffafa; }
.btn-block { width: 100%; margin-top: 25px; }
.login-help { margin-top: 22px; padding: 12px; border-radius: 8px; background: #f3f8f7; color: #5d747d; font-size: 12px; line-height: 1.6; }
.app-shell { min-height: 100vh; display: grid; grid-template-columns: 236px 1fr; }
.sidebar { background: var(--navy); color: #d3e7e7; padding: 25px 16px; display: flex; flex-direction: column; gap: 32px; }
.sidebar .brand { color: white; padding: 0 8px; }
.nav { display:grid; gap: 6px; }
.nav button { border: 0; text-align: left; padding: 11px 12px; border-radius: 8px; color: #b7d1d4; background: transparent; font-weight: 600; }
.nav button:hover, .nav button.active { background: rgba(255,255,255,.12); color: white; }
.sidebar-bottom { margin-top: auto; display:grid; gap: 12px; padding: 8px; font-size: 13px; }
.sidebar-bottom strong { display:block; color:white; }
.logout { background:transparent; border:0; color:#a9c7cb; padding:0; text-align:left; }
.main { min-width: 0; padding: 32px clamp(20px, 4vw, 60px) 54px; }
.topline { display:flex; justify-content:space-between; align-items:flex-start; gap:20px; margin-bottom: 27px; }
.topline h1 { margin: 5px 0 0; font: 600 clamp(27px, 3vw, 38px) Georgia, "Songti SC", serif; letter-spacing: .02em; }
.date-label { color: var(--muted); font-size: 13px; padding-top:10px; }
.metric-grid { display:grid; grid-template-columns:repeat(4,minmax(0,1fr)); gap:15px; margin-bottom:28px; }
.metric { padding: 19px; border:1px solid var(--line); background:var(--white); border-radius:13px; }
.metric span { font-size:12px; font-weight:700; color:var(--muted); }
.metric strong { display:block; margin-top:8px; font: 500 31px Georgia, serif; color:var(--navy); }
.content-grid { display:grid; grid-template-columns: minmax(0, 1.4fr) minmax(270px,.7fr); gap:20px; }
.panel { background:var(--white); border:1px solid var(--line); border-radius:13px; overflow:hidden; }
.panel-head { padding:18px 21px; display:flex; align-items:center; justify-content:space-between; gap:16px; border-bottom:1px solid var(--line); }
.panel-head h2 { margin:0; font:600 21px Georgia, "Songti SC", serif; }
.panel-body { padding: 18px 21px; }
.session-row { display:grid; grid-template-columns: 1fr auto; gap:12px; padding:15px 0; border-bottom:1px solid #edf2f1; }
.session-row:last-child { border-bottom:0; }
.session-row h3 { margin:0 0 5px; font-size:15px; }
.session-row p { margin:0; font-size:12px; color:var(--muted); }
.badge { display:inline-flex; align-items:center; min-height:22px; padding:0 8px; border-radius:20px; background:#edf7f4; color:#27725f; font-size:11px; font-weight:700; }
.badge.live { background:#fff2d9; color:#a56305; }
.lesson-list { display:grid; grid-template-columns:repeat(auto-fill,minmax(245px,1fr)); gap:16px; }
.lesson-card { min-height:220px; padding:20px; background:var(--white); border:1px solid var(--line); border-radius:13px; display:flex; flex-direction:column; }
.lesson-card .eyebrow { color:#5e909f; letter-spacing:.08em; text-transform:none; }
.lesson-card h2 { margin:12px 0 8px; font:600 23px/1.25 Georgia, "Songti SC", serif; }
.lesson-card p { color:var(--muted); font-size:13px; line-height:1.65; margin:0; }
.lesson-card footer { margin-top:auto; padding-top:17px; display:flex; justify-content:space-between; align-items:center; color:var(--muted); font-size:12px; }
.tool-row { display:flex; flex-wrap:wrap; gap:8px; }
.empty { color:var(--muted); text-align:center; padding:38px 15px; line-height:1.7; }
.form-grid { display:grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: 0 16px; }
.form-span { grid-column:1/-1; }
.board-editor { margin-top:23px; border:1px solid var(--line); border-radius:10px; padding:15px; background:#f9fcfb; }
.board-editor h3 { margin:0 0 10px; font-size:15px; }
.board-editor-row { display:grid; grid-template-columns:70px 1fr 1.35fr auto; align-items:center; gap:8px; padding:8px 0; border-bottom:1px dashed #dbe7e7; }
.board-editor-row input { min-width:0; padding:8px; border:1px solid #ccdadd; border-radius:7px; }
.icon-btn { border:0; color:var(--muted); background:transparent; padding:6px; font-size:18px; }
.modal-backdrop { position:fixed; inset:0; z-index:20; background:rgba(15,42,55,.46); display:grid; place-items:center; padding:18px; }
.modal { width:min(680px,100%); max-height:90vh; overflow:auto; border-radius:15px; background:white; box-shadow:0 25px 65px rgba(0,0,0,.2); }
.modal .panel-head { position:sticky; top:0; background:white; z-index:1; }
.modal .panel-body { padding:20px 24px 25px; }
.modal-actions { display:flex; justify-content:flex-end; gap:10px; margin-top:22px; }
.checkboxes { display:flex; flex-wrap:wrap; gap:8px 14px; padding:11px; border:1px solid var(--line); border-radius:9px; min-height:44px; }
.checkboxes label { font-size:13px; color:#466270; }
.textbook-list { display:grid; grid-template-columns:repeat(auto-fill,minmax(230px,1fr)); gap:12px; }
.textbook-card { border:1px solid var(--line); background:white; border-radius:11px; padding:16px; }
.textbook-card strong { font-size:15px; }
.textbook-card p { color:var(--muted); font-size:12px; line-height:1.55; }

/* 课堂演示 */
.classroom { height:100vh; min-height:600px; background:#101f28; color:#eef7f4; display:grid; grid-template-rows:64px 1fr 42px; overflow:hidden; }
.classroom-top { display:flex; align-items:center; gap:16px; padding:0 19px; background:#163447; border-bottom:1px solid rgba(255,255,255,.11); }
.classroom-top .title-block { min-width:0; flex:1; }
.classroom-top h1 { margin:0; font-size:16px; white-space:nowrap; overflow:hidden; text-overflow:ellipsis; }
.classroom-top small { color:#a8c5ca; font-size:12px; }
.timer { font:500 21px ui-monospace, SFMono-Regular, monospace; padding:6px 12px; border-left:1px solid rgba(255,255,255,.15); border-right:1px solid rgba(255,255,255,.15); }
.classroom-top .btn { min-height:34px; font-size:12px; }
.classroom-main { min-height:0; display:grid; grid-template-columns:minmax(0, 1fr) minmax(245px, 24vw); }
.stage { position:relative; min-width:0; overflow:hidden; background:#26323a; display:grid; place-items:center; }
.pdf-frame { position:absolute; inset:0; width:100%; height:100%; border:0; background:white; }
.pdf-frame.ink-active { pointer-events:none; }
.mock-slide { width:min(91%, 1000px); aspect-ratio:16/9; color:#193648; padding:clamp(27px,5vw,75px); background:#fffefa; box-shadow:0 15px 43px rgba(0,0,0,.3); position:relative; overflow:hidden; }
.mock-slide::after { content:""; position:absolute; width:270px; height:270px; border:1px solid #d4eced; border-radius:50%; right:-110px; bottom:-105px; }
.mock-slide .slide-index { color:#5b8c98; font-weight:700; letter-spacing:.13em; font-size:clamp(11px,1vw,15px); }
.mock-slide h2 { margin:clamp(17px,5vw,58px) 0 15px; position:relative; z-index:1; font:600 clamp(30px,4vw,65px)/1.15 Georgia, "Songti SC", serif; }
.mock-slide p { max-width:75%; position:relative; z-index:1; font-size:clamp(15px,1.7vw,23px); line-height:1.85; color:#46616e; }
.formula-big { display:inline-block; margin-top:14px; padding:14px 19px; border-left:4px solid var(--gold); background:#fcf6e8; font:500 clamp(23px,3vw,44px) Georgia, serif; }
.ink-canvas { position:absolute; inset:0; width:100%; height:100%; z-index:5; pointer-events:none; }
.ink-canvas.active { pointer-events:auto; cursor:crosshair; }
.stage-toolbar { position:absolute; z-index:8; left:50%; transform:translateX(-50%); bottom:17px; display:flex; gap:6px; padding:6px; border-radius:11px; background:rgba(17,48,64,.92); box-shadow:0 8px 24px rgba(0,0,0,.24); }
.stage-toolbar button { border:1px solid transparent; border-radius:7px; color:#d5e5e4; background:transparent; padding:7px 9px; font-size:12px; }
.stage-toolbar button.active { background:#347a95; color:white; }
.stage-toolbar .divider { width:1px; background:rgba(255,255,255,.2); margin:3px; }
.board-panel { display:grid; min-height:0; grid-template-rows:auto minmax(0,1fr) 43%; border-left:1px solid rgba(255,255,255,.13); background:#f8fbf6; color:var(--ink); }
.board-head { padding:15px 15px 11px; border-bottom:1px solid #dae5e4; display:flex; align-items:flex-start; justify-content:space-between; gap:8px; }
.board-head h2 { margin:1px 0 0; font:600 21px Georgia, "Songti SC", serif; }
.board-head p { margin:3px 0 0; color:var(--muted); font-size:11px; }
.board-list { overflow:auto; padding:12px 13px; display:grid; align-content:start; gap:9px; background:linear-gradient(90deg, transparent 23px, #e2edec 24px, transparent 25px); }
.board-empty { padding:23px 13px; color:#81939a; font-size:13px; line-height:1.6; text-align:center; }
.board-card { position:relative; padding:10px 10px 10px 14px; border-radius:7px; background:white; border:1px solid #dfe9e8; box-shadow:0 2px 5px rgba(25,59,72,.04); }
.board-card::before { content:""; position:absolute; left:0; top:0; bottom:0; width:4px; border-radius:6px 0 0 6px; background:#75aab5; }
.board-card.key::before { background:#e2a63e; }.board-card.warning::before { background:#cf7566; }
.board-card h3 { margin:0 0 5px; font-size:12px; color:#476471; }
.board-card .latex { color:#173f54; font:600 18px Georgia, "Times New Roman", serif; line-height:1.4; word-break:break-word; }
.frac { display:inline-grid; grid-template-rows:auto auto; vertical-align:middle; margin:0 .08em; line-height:1.02; text-align:center; font-size:.86em; }
.frac > span:first-child { border-bottom:1.5px solid currentColor; padding:0 .16em .04em; }.frac > span:last-child { padding:.04em .16em 0; }
.board-card p { margin:5px 0 0; color:#607982; font-size:11px; line-height:1.45; }
.manual-note { font:500 15px/1.5 Georgia, "Songti SC", serif; color:#264e61; }
.whiteboard { position:relative; min-height:0; overflow:hidden; border-top:1px solid #cbdcde; background-color:#fffcf5; background-image:radial-gradient(#c3d4d2 1px, transparent 1.1px); background-size:17px 17px; }
.whiteboard-label { position:absolute; z-index:2; top:8px; left:11px; color:#73888c; font-size:11px; font-weight:700; pointer-events:none; }
.board-canvas { position:absolute; inset:0; width:100%; height:100%; z-index:1; pointer-events:none; }.board-canvas.active { pointer-events:auto; cursor:crosshair; }
.board-controls { position:absolute; z-index:3; right:8px; bottom:7px; display:flex; gap:4px; }.board-controls button { font-size:11px; min-height:27px; padding:0 7px; border-radius:6px; border:1px solid #cadcdb; background:rgba(255,255,255,.9); color:#476874; }
.classroom-footer { display:flex; justify-content:space-between; align-items:center; padding:0 20px; color:#9dbdc0; background:#132c3b; font-size:12px; }.classroom-footer strong { color:#f6cb6d; }
.summary-box { padding: 19px; background:#fff; border-top:1px solid var(--line); }.summary-box textarea { min-height:66px; }
#toast-root { position:fixed; z-index:50; top:18px; right:18px; display:grid; gap:8px; }.toast { color:white; background:#183d53; box-shadow:var(--shadow); border-radius:9px; padding:11px 14px; font-size:13px; animation:in .2s ease-out; }.toast.error{background:#a8453d}@keyframes in{from{opacity:0;transform:translateY(-8px)}to{opacity:1;transform:translateY(0)}}
@media (max-width: 800px) { .login-shell { grid-template-columns:1fr; }.login-art{padding:30px; min-height:300px}.login-art h1{margin:50px 0 13px;font-size:37px}.login-points{display:none}.app-shell{grid-template-columns:1fr}.sidebar{padding:13px;gap:13px}.sidebar .brand{display:none}.nav{display:flex;overflow:auto}.nav button{white-space:nowrap}.sidebar-bottom{display:none}.main{padding:25px 17px}.metric-grid{grid-template-columns:repeat(2,1fr)}.content-grid{grid-template-columns:1fr}.form-grid{grid-template-columns:1fr}.classroom-main{grid-template-columns:1fr;grid-template-rows:60% 40%}.board-panel{grid-template-columns:1fr 1fr;grid-template-rows:auto 1fr}.board-head{grid-column:1/-1}.whiteboard{border-top:0;border-left:1px solid #cbdcde}.classroom-top{gap:8px;padding:0 9px}.timer{font-size:14px;padding:5px}.classroom-top .btn-soft{display:none}.stage-toolbar{max-width:95%;overflow:auto;left:9px;transform:none;bottom:9px}.stage-toolbar button{white-space:nowrap}.classroom{min-height:570px}.board-editor-row{grid-template-columns:50px 1fr auto}.board-editor-row input:nth-child(3){grid-column:2/3}.date-label{display:none} }