:root{
  --bg:#F7F8FA; --surface:#FFFFFF; --border:#E5E7EB; --border-2:#D1D5DB;
  --text:#111827; --muted:#6B7280; --faint:#9CA3AF;
  --green:#15803D; --green-bg:#DCFCE7; --green-fill:#22C55E;
  --amber:#B45309; --amber-bg:#FEF3C7; --amber-fill:#F59E0B;
  --red:#B91C1C; --red-bg:#FEE2E2;
  --blue:#1D4ED8; --blue-bg:#DBEAFE;
  --radius:12px; --shadow:0 1px 2px rgba(16,24,40,.04),0 1px 3px rgba(16,24,40,.06);
  --font:"Inter",-apple-system,"Segoe UI",system-ui,sans-serif;
}
*{box-sizing:border-box}
html,body{margin:0;height:100%}
body{background:var(--bg);color:var(--text);font:400 15px/1.5 var(--font);-webkit-font-smoothing:antialiased}
[hidden]{display:none!important}
a{color:inherit;text-decoration:none}
button{font:inherit;color:inherit;cursor:pointer}
h1{font-size:26px;line-height:1.2;font-weight:700;letter-spacing:-.02em;margin:0}
h2{font-size:17px;font-weight:600;margin:0}
.muted{color:var(--muted)} .faint{color:var(--faint)}
.small{font-size:13px}
.mono{font-family:ui-monospace,"SF Mono",Menlo,Consolas,monospace;font-size:12.5px}

/* header */
.header{position:sticky;top:0;z-index:20;background:var(--surface);border-bottom:1px solid var(--border)}
.header-in{max-width:1120px;margin:0 auto;height:60px;padding:0 24px;display:flex;align-items:center;gap:28px}
.logo{display:flex;align-items:center;gap:10px;font-weight:700;font-size:16px;letter-spacing:-.01em}
.logo i{display:grid;place-items:center;width:28px;height:28px;border-radius:8px;background:var(--text);color:#fff;font-style:normal;font-size:14px;font-weight:700}
.logo span{color:var(--muted);font-weight:500;padding-left:10px;border-left:1px solid var(--border)}
.nav{display:flex;gap:4px}
.nav a{padding:7px 12px;border-radius:8px;font-weight:500;color:var(--muted)}
.nav a:hover{color:var(--text);background:var(--bg)}
.nav a.on{color:var(--text);background:var(--bg)}
.grow{flex:1}
.user{display:flex;align-items:center;gap:10px;font-size:14px}
.avatar{display:grid;place-items:center;width:32px;height:32px;border-radius:50%;background:#EEF0F3;color:var(--text);font-weight:600;font-size:12.5px;flex:0 0 auto}
.avatar.lg{width:48px;height:48px;font-size:17px}

.page{max-width:1120px;margin:0 auto;padding:32px 24px 80px}
.page-head{display:flex;align-items:center;gap:16px;margin-bottom:24px;flex-wrap:wrap}
.crumbs{font-size:14px;color:var(--muted);margin-bottom:10px}
.crumbs a:hover{color:var(--text)}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;height:36px;padding:0 14px;border-radius:8px;border:1px solid var(--border-2);background:var(--surface);font-weight:500;font-size:14px;white-space:nowrap;transition:background .15s,border-color .15s}
.btn:hover{background:var(--bg)}
.btn.primary{background:var(--text);border-color:var(--text);color:#fff}
.btn.primary:hover{background:#1F2937}
.btn.ghost{border-color:transparent;background:transparent;color:var(--muted)}
.btn.ghost:hover{background:var(--bg);color:var(--text)}
.btn.danger{color:var(--red)}
.btn.danger:hover{background:var(--red-bg);border-color:#FCA5A5}
.btn.sm{height:30px;padding:0 10px;font-size:13px}
.btn.icon{width:34px;padding:0}
.btn:disabled{opacity:.5;cursor:default}

/* cards, badges, bars */
.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow)}
.card.pad{padding:20px 24px}
.badge{display:inline-flex;align-items:center;gap:5px;height:24px;padding:0 9px;border-radius:999px;font-size:12.5px;font-weight:500;white-space:nowrap;background:#F3F4F6;color:var(--muted)}
.badge.green{background:var(--green-bg);color:var(--green)}
.badge.amber{background:var(--amber-bg);color:var(--amber)}
.badge.red{background:var(--red-bg);color:var(--red)}
.badge.blue{background:var(--blue-bg);color:var(--blue)}
.bar{height:6px;border-radius:999px;background:#EEF0F3;overflow:hidden;min-width:60px}
.bar i{display:block;height:100%;background:var(--text);border-radius:999px}
.bar.green i{background:var(--green-fill)}
.num{font-weight:600;font-variant-numeric:tabular-nums}
.num.green{color:var(--green)} .num.amber{color:var(--amber)} .num.red{color:var(--red)}

/* table */
.table{width:100%;border-collapse:separate;border-spacing:0}
.table th{text-align:left;font-size:12.5px;font-weight:500;color:var(--muted);padding:12px 16px;border-bottom:1px solid var(--border)}
.table td{padding:14px 16px;border-bottom:1px solid var(--border);vertical-align:middle;font-size:14px}
.table tr:last-child td{border-bottom:0}
.table tr.link{cursor:pointer}
.table tr.link:hover td{background:#FAFAFB}
.who{display:flex;align-items:center;gap:12px}
.who b{display:block;font-weight:600}
.cell-sub{font-size:12.5px;color:var(--muted)}
.prog{display:flex;align-items:center;gap:10px}
.prog .bar{width:110px}

/* empty */
.empty{padding:48px 24px;text-align:center;color:var(--muted)}
.empty b{display:block;color:var(--text);font-size:16px;margin-bottom:4px}

/* login */
.login-wrap{min-height:100vh;display:grid;place-items:center;padding:24px}
.login{width:100%;max-width:380px;padding:32px}
.login .logo{margin-bottom:24px}
.field{display:grid;gap:6px;margin-bottom:14px}
.field label{font-size:13px;font-weight:500;color:var(--muted)}
.input{height:40px;padding:0 12px;border:1px solid var(--border-2);border-radius:8px;background:var(--surface);font:inherit;font-size:15px;width:100%}
.input:focus{outline:none;border-color:var(--text);box-shadow:0 0 0 3px rgba(17,24,39,.08)}
.error{color:var(--red);font-size:13px;min-height:18px;margin-top:6px}

/* student home */
.continue{display:flex;align-items:center;gap:24px;padding:24px;margin-bottom:28px;flex-wrap:wrap}
.continue .label{font-size:12.5px;color:var(--muted);margin-bottom:4px}
.continue .big{font-size:22px;font-weight:700;letter-spacing:-.01em}
.continue .meta{display:flex;gap:18px;margin-top:8px;font-size:14px;color:var(--muted);flex-wrap:wrap}
.continue .acts{display:flex;gap:8px;margin-left:auto}
.unit-card{margin-bottom:12px;overflow:hidden}
.unit-head{display:flex;align-items:center;gap:14px;padding:16px 20px;cursor:pointer}
.unit-head .u{font-size:12.5px;font-weight:600;color:var(--muted);width:54px}
.unit-head h2{flex:1}
.unit-head .prog .bar{width:90px}
.unit-card.locked .unit-head{cursor:default}
.unit-card.locked h2{color:var(--faint)}
.lessons{border-top:1px solid var(--border)}
.lesson-row{display:flex;align-items:center;gap:14px;padding:12px 20px;border-bottom:1px solid var(--border)}
.lesson-row:last-child{border-bottom:0}
a.lesson-row:hover{background:#FAFAFB}
.lesson-row .ico{width:26px;height:26px;border-radius:50%;display:grid;place-items:center;flex:0 0 auto;font-size:13px;font-weight:600;border:1.5px solid var(--border-2);color:var(--muted)}
.lesson-row.passed .ico{background:var(--green-fill);border-color:var(--green-fill);color:#fff}
.lesson-row.open .ico{border-color:var(--text);color:var(--text)}
.lesson-row.locked{color:var(--faint)}
.lesson-row .ttl{flex:1;min-width:0}
.lesson-row .ttl b{font-weight:600}
.lesson-row .ttl span{color:var(--muted);margin-left:6px}
.lesson-row.locked .ttl span{color:var(--faint)}

/* frame pages (lesson, preview, live) */
.frame-page{height:100vh;display:flex;flex-direction:column}
.subbar{background:var(--surface);border-bottom:1px solid var(--border)}
.subbar-in{max-width:none;height:56px;padding:0 20px;display:flex;align-items:center;gap:16px}
.subbar .path{font-size:14px;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.subbar .path b{color:var(--text);font-weight:600}
.tabs{display:inline-flex;padding:3px;border-radius:10px;background:#F1F2F4;gap:2px}
.tabs button{height:30px;padding:0 12px;border:0;border-radius:8px;background:transparent;font-size:13.5px;font-weight:500;color:var(--muted);display:inline-flex;align-items:center;gap:6px}
.tabs button.on{background:var(--surface);color:var(--text);box-shadow:var(--shadow)}
.tabs button .cnt{font-size:12px;color:var(--faint)}
.frame-body{flex:1;display:flex;min-height:0}
.frame-body iframe{flex:1;border:0;min-width:0;background:#E9EDF2}
.toast{display:flex;align-items:center;gap:12px;padding:10px 20px;background:var(--green-bg);color:var(--green);font-size:14px;font-weight:500;border-bottom:1px solid #BBF7D0}
.toast .btn{height:30px}

/* side panel with results */
.side{width:380px;flex:0 0 380px;border-left:1px solid var(--border);background:var(--surface);overflow:auto;padding:20px}
.side h3{font-size:13px;font-weight:600;margin:22px 0 4px;display:flex;align-items:center;gap:8px}
@media (max-width:980px){.side{display:none}}

/* exercise rows */
.ex{display:flex;gap:12px;padding:12px 0;border-bottom:1px solid var(--border)}
.ex:last-child{border-bottom:0}
.ex .st{width:22px;height:22px;border-radius:50%;flex:0 0 auto;display:grid;place-items:center;font-size:12px;font-weight:700;margin-top:1px;background:#F3F4F6;color:var(--faint)}
.ex .st.green{background:var(--green-bg);color:var(--green)}
.ex .st.amber{background:var(--amber-bg);color:var(--amber)}
.ex .st.red{background:var(--red-bg);color:var(--red)}
.ex .body{flex:1;min-width:0}
.ex .t{font-size:14px;line-height:1.4}
.ex .r{font-size:13px;margin-top:3px;color:var(--muted)}
.ex .r b{font-weight:600;color:var(--text)}
.ex .tags{display:flex;gap:6px;margin-top:6px;flex-wrap:wrap}
.ex.fresh{animation:fresh 2.5s ease-out}
@keyframes fresh{from{background:var(--green-bg)}to{background:transparent}}
.none{font-size:13px;color:var(--faint);padding:10px 0}

/* teacher: student page */
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;margin-bottom:28px}
.stat{padding:16px 18px}
.stat .k{font-size:13px;color:var(--muted)}
.stat .v{font-size:24px;font-weight:700;letter-spacing:-.02em;margin-top:2px}
.stat .v small{font-size:14px;font-weight:500;color:var(--muted)}
@media (max-width:820px){.stats{grid-template-columns:repeat(2,1fr)}}
.section-head{display:flex;align-items:center;gap:16px;margin:0 0 12px;flex-wrap:wrap}
.legend{display:flex;gap:14px;font-size:12.5px;color:var(--muted);flex-wrap:wrap}
.legend i{display:inline-block;width:12px;height:12px;border-radius:4px;vertical-align:-2px;margin-right:5px;border:1.5px solid var(--border-2)}
.legend i.g{background:var(--green-fill);border-color:var(--green-fill)} .legend i.o{border-color:var(--text)} .legend i.h{width:14px;height:4px;border:0;background:var(--amber-fill);vertical-align:2px}
.map{padding:6px 20px;display:grid;grid-template-columns:1fr 1fr;column-gap:32px}
@media (max-width:980px){.map{grid-template-columns:1fr}}
.map-row{display:flex;align-items:center;gap:14px;padding:10px 0;border-bottom:1px solid var(--border)}
.map-row:nth-last-child(-n+2){border-bottom:0}
.map-row .name{width:140px;flex:0 0 auto;font-size:14px;line-height:1.3}
.map-row .name span{color:var(--muted);font-size:12.5px;display:block}
.cells{display:flex;gap:6px;flex-wrap:wrap}
.cell{width:34px;display:grid;gap:4px;background:none;border:0;padding:0}
.cell .sq{height:30px;border-radius:8px;display:grid;place-items:center;font-size:13px;font-weight:600;border:1.5px solid var(--border);background:#FAFAFB;color:var(--faint)}
.cell.open .sq{border-color:var(--text);background:var(--surface);color:var(--text)}
.cell.passed .sq{background:var(--green-fill);border-color:var(--green-fill);color:#fff}
.cell .hw{height:4px;border-radius:2px;background:transparent}
.cell .hw.part{background:var(--amber-fill)} .cell .hw.full{background:var(--green-fill)} .cell .hw.no{background:#E5E7EB}
.cell.sel .sq{box-shadow:0 0 0 2px var(--surface),0 0 0 4px var(--text)}
.detail{margin-top:20px}
.detail-head{display:flex;align-items:center;gap:12px;padding:18px 24px;border-bottom:1px solid var(--border);flex-wrap:wrap}
.detail-cols{display:grid;grid-template-columns:1fr 1fr}
.detail-cols>div{padding:8px 24px 16px}
.detail-cols>div+div{border-left:1px solid var(--border)}
.detail-cols h3{font-size:13px;font-weight:600;margin:12px 0 2px;display:flex;align-items:center;gap:8px}
@media (max-width:820px){.detail-cols{grid-template-columns:1fr}.detail-cols>div+div{border-left:0;border-top:1px solid var(--border)}}

/* teacher: textbooks */
.books{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:16px}
.book-card{display:block;overflow:hidden;transition:transform .15s,box-shadow .15s}
.book-card:hover{transform:translateY(-2px);box-shadow:0 8px 24px rgba(16,24,40,.10)}
.cover-img{display:block;width:100%;aspect-ratio:480/679;object-fit:cover;border-bottom:1px solid var(--border)}
.book-meta{padding:14px 16px;display:grid;gap:2px}
.book-meta b{font-size:16px}
.book-meta span{font-size:13px;color:var(--muted)}
.cover-sm{width:56px;height:79px;object-fit:cover;border-radius:6px;border:1px solid var(--border);box-shadow:var(--shadow)}
a.ucard{display:block;transition:border-color .15s,box-shadow .15s}
a.ucard:hover{border-color:var(--border-2);box-shadow:0 6px 18px rgba(16,24,40,.08)}
.ulessons{display:flex;flex-wrap:wrap;gap:4px 14px;font-size:13px;color:var(--muted)}
.select{height:34px;padding:0 30px 0 12px;border:1px solid var(--border-2);border-radius:8px;background:var(--surface) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath d='M3 4.5l3 3 3-3' fill='none' stroke='%236B7280' stroke-width='1.5'/%3E%3C/svg%3E") no-repeat right 10px center;-webkit-appearance:none;appearance:none;font:inherit;font-size:13.5px;font-weight:500;cursor:pointer}
/* teacher: book (old) */
.book{display:flex;align-items:center;gap:20px;padding:24px;margin-bottom:20px}
.book .cover{width:56px;height:72px;border-radius:6px;background:linear-gradient(160deg,#1F2937,#4B5563);color:#fff;display:flex;flex-direction:column;justify-content:flex-end;padding:8px;font-weight:700;font-size:20px;line-height:1}
.book .cover small{font-size:8.5px;font-weight:600;letter-spacing:.06em;text-transform:uppercase;opacity:.8;margin-bottom:3px}
.units-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:12px}
@media (max-width:820px){.units-grid{grid-template-columns:1fr}}
.ucard{padding:18px 20px}
.ucard .top{display:flex;align-items:baseline;gap:10px;margin-bottom:12px}
.ucard .top .u{font-size:12.5px;font-weight:600;color:var(--muted)}
.ucard .links{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:12px}
.ucard .links a{font-size:13px;padding:4px 9px;border-radius:7px;background:#F3F4F6;color:var(--text)}
.ucard .links a:hover{background:#E5E7EB}
.ucard .acts{display:flex;gap:8px}

/* modal */
.overlay{position:fixed;inset:0;background:rgba(17,24,39,.35);display:grid;place-items:center;z-index:50;padding:20px}
.modal{width:100%;max-width:420px;padding:24px}
.modal h2{margin-bottom:18px}
.modal .acts{display:flex;justify-content:flex-end;gap:8px;margin-top:8px}
.copybox{background:var(--bg);border:1px solid var(--border);border-radius:8px;padding:12px 14px;font-size:14px;margin:4px 0 14px}