/* Palette lifted from public/css/design-system.css so the course site and the
   tutor read as one product. Dark is the default, as it is in the app. */
:root{
  --bg:#0B0F1A; --panel:#161B2C; --panel-2:#1B2238;
  --ink:#E6E9F2; --muted:#9AA3B8;
  --line:rgba(255,255,255,.08); --line-strong:rgba(255,255,255,.18);
  --accent:#8B7BFF; --accent-strong:#6C5CE7; --accent-soft:rgba(139,123,255,.14);
  --ok:#2ECC71; --ok-soft:rgba(46,204,113,.14);
  --warn:#FFD66B; --warn-soft:rgba(255,214,107,.14);
  --radius:18px;
  --shadow:0 8px 20px rgba(0,0,0,.38);
}
@media (prefers-color-scheme:light){
  :root{
    --bg:#F5F7FB; --panel:#FFFFFF; --panel-2:#EEF1F7;
    --ink:#18202B; --muted:#5B6876;
    --line:rgba(16,24,40,.10); --line-strong:rgba(16,24,40,.18);
    --accent:#6C5CE7; --accent-strong:#5A4BD1; --accent-soft:#EDE9FF;
    --ok:#1a8f5a; --ok-soft:#E3F5EC;
    --warn:#B45309; --warn-soft:#FDF0DC;
    --shadow:0 1px 2px rgba(16,24,40,.05),0 8px 20px rgba(16,24,40,.07);
  }
}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);
  font:16px/1.55 ui-sans-serif,-apple-system,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  -webkit-text-size-adjust:100%}
a{color:inherit}
.wrap{max-width:940px;margin:0 auto;padding:28px 20px 72px}

/* top bar */
.topbar{position:sticky;top:0;z-index:20;display:flex;align-items:center;
  justify-content:space-between;gap:12px;padding:10px 20px;
  background:color-mix(in srgb,var(--panel) 88%,transparent);
  backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none}
.brand-logo{height:30px;width:auto;display:block}
@media(max-width:520px){.brand-logo{height:26px}}
.brand span span,.brand>span{display:flex;flex-direction:column;line-height:1.15}
.brand em{font-style:normal;font-size:12px;color:var(--muted)}
.chip{font-size:13px;color:var(--muted);border:1px solid var(--line);
  padding:4px 10px;border-radius:999px}
.topbar-right{display:flex;align-items:center;gap:10px}
.tutor-top{display:inline-flex;align-items:center;gap:6px;font-size:13.5px;font-weight:600;
  text-decoration:none;color:#fff;
  background:linear-gradient(135deg,var(--accent),var(--accent-strong));padding:7px 14px;border-radius:999px;
  white-space:nowrap;transition:.15s}
.tutor-top:hover{filter:brightness(1.08)}
@media(max-width:520px){.chip{display:none}}

/* per-lesson tutor hand-off */
.tutor-cta{display:flex;align-items:center;gap:12px;margin-top:12px;padding:12px 14px;
  border-radius:11px;text-decoration:none;color:inherit;background:var(--accent-soft);
  border:1px solid transparent;transition:.15s}
.tutor-cta:hover{border-color:var(--accent)}
.tutor-ic{flex:none;display:grid;place-items:center;width:32px;height:32px;border-radius:9px;
  background:linear-gradient(135deg,var(--accent),var(--accent-strong));color:#fff;font-size:15px}
.tutor-txt{display:flex;flex-direction:column;line-height:1.3;min-width:0}
.tutor-txt b{font-size:14.5px;color:var(--accent)}
.tutor-txt em{font-style:normal;font-size:12.5px;color:var(--muted)}
.tutor-go{margin-left:auto;color:var(--accent);font-size:18px}

/* hero */
.hero{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);
  padding:30px;box-shadow:var(--shadow);margin-bottom:30px}
.hero h1{margin:0 0 8px;font-size:clamp(28px,5vw,40px);letter-spacing:-.02em}
.lede{margin:0 0 22px;color:var(--muted);max-width:60ch}
.stats{display:flex;flex-wrap:wrap;gap:26px;padding-top:20px;border-top:1px solid var(--line)}
.stats div{display:flex;flex-direction:column}
.stats b{font-size:24px;letter-spacing:-.02em}
.stats span{font-size:13px;color:var(--muted)}
.overall{margin-top:20px}

/* progress bars */
.bar{height:7px;border-radius:99px;background:var(--line);overflow:hidden;margin:10px 0 6px}
.bar.big{height:9px}
.bar-fill{display:block;height:100%;width:0;border-radius:99px;background:var(--ok);
  transition:width .35s ease}
.ch-prog{margin:0;font-size:12.5px;color:var(--muted)}

/* chapter grid */
.section-head{font-size:14px;text-transform:uppercase;letter-spacing:.09em;
  color:var(--muted);margin:0 0 14px}
.ch-grid{display:grid;gap:14px;grid-template-columns:repeat(auto-fill,minmax(290px,1fr))}
.ch-card{display:flex;gap:16px;text-decoration:none;background:var(--panel);
  border:1px solid var(--line);border-radius:var(--radius);padding:18px;
  box-shadow:var(--shadow);transition:transform .15s ease,border-color .15s ease}
.ch-card:hover{transform:translateY(-2px);border-color:var(--accent)}
.ch-num{flex:none;width:42px;height:42px;border-radius:11px;display:grid;place-items:center;
  background:var(--accent-soft);color:var(--accent);font-weight:700;font-size:17px}
.ch-body{min-width:0;flex:1}
.ch-body h3{margin:2px 0 4px;font-size:16.5px;letter-spacing:-.01em}
.ch-meta{margin:0;font-size:13px;color:var(--muted)}

/* chapter page */
.ch-head{margin-bottom:24px}
.crumb{margin:0 0 10px;font-size:13px}
.crumb a{color:var(--accent);text-decoration:none}
.ch-head h1{display:flex;align-items:center;gap:14px;margin:0 0 6px;
  font-size:clamp(23px,4vw,32px);letter-spacing:-.02em}
.big-num{flex:none;display:grid;place-items:center;width:46px;height:46px;border-radius:12px;
  background:linear-gradient(135deg,var(--accent),var(--accent-strong));color:#fff;font-size:20px}
.toc{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);
  padding:16px 18px;margin-bottom:26px;box-shadow:var(--shadow)}
.toc h4{margin:0 0 10px;font-size:12px;text-transform:uppercase;letter-spacing:.08em;
  color:var(--muted)}
.toc-links{display:grid;gap:2px}
.toc-links a{display:flex;gap:10px;padding:5px 8px;border-radius:8px;font-size:14px;
  text-decoration:none;color:var(--ink)}
.toc-links a:hover{background:var(--accent-soft);color:var(--accent)}
.toc-links span{color:var(--muted);min-width:20px;font-variant-numeric:tabular-nums}

/* lesson */
.lesson{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);
  padding:20px;margin-bottom:16px;box-shadow:var(--shadow);scroll-margin-top:76px}
.lesson.done{border-color:var(--ok)}
.lesson.done .lesson-title h3{color:var(--muted);text-decoration:line-through}
.lesson-head{display:flex;gap:14px;align-items:flex-start}
.lesson-title{min-width:0}
.daynum{margin:0;font-size:12px;color:var(--muted);text-transform:uppercase;
  letter-spacing:.07em}
.lesson-title h3{margin:3px 0 8px;font-size:19px;letter-spacing:-.01em}
.badges{display:flex;flex-wrap:wrap;gap:6px}
.badge{font-size:11.5px;padding:3px 9px;border-radius:999px;border:1px solid var(--line);
  color:var(--muted);white-space:nowrap}
.badge.k-test{background:var(--warn-soft);color:var(--warn);border-color:transparent;font-weight:600}
.badge.k-quiz{background:var(--warn-soft);color:var(--warn);border-color:transparent}
.badge.k-review{background:var(--accent-soft);color:var(--accent);border-color:transparent}
.badge.sec{font-variant-numeric:tabular-nums;font-weight:600;color:var(--ink)}
.badge.due{background:var(--ok-soft);color:var(--ok);border-color:transparent}

/* checkbox */
.check{flex:none;cursor:pointer;position:relative;width:26px;height:26px;margin-top:3px}
.check input{position:absolute;inset:0;opacity:0;cursor:pointer;margin:0}
.check span{position:relative;display:block;width:26px;height:26px;border-radius:8px;
  border:2px solid var(--line);transition:.15s}
.check input:checked+span{background:var(--ok);border-color:var(--ok)}
.check input:checked+span::after{content:"";position:absolute;left:7px;top:2px;width:6px;
  height:12px;border:solid #fff;border-width:0 2.5px 2.5px 0;transform:rotate(42deg)}
/* On touch, grow the hit area to the 44px minimum without moving the visual
   box — otherwise the check is a 26px target and a thumb misses it. */
@media(pointer:coarse){
  .check input{inset:auto;left:-9px;top:-9px;width:44px;height:44px}
}
.check input:focus-visible+span{outline:2px solid var(--accent);outline-offset:2px}

.lesson-body{padding-left:40px}
@media(max-width:560px){.lesson-body{padding-left:0}}

/* media */
.videos{display:grid;gap:14px;margin:14px 0}
.video{margin:0}
.video video{width:100%;border-radius:10px;background:#000;display:block;aspect-ratio:16/10}
.video figcaption{font-size:12.5px;color:var(--muted);margin-top:6px}
.pending-box{display:flex;align-items:center;justify-content:center;gap:10px;flex-wrap:wrap;
  min-height:64px;border-radius:10px;border:1px dashed var(--line-strong);background:var(--panel-2);
  text-align:center;padding:14px 16px}
.pending-box span{font-size:14px;color:var(--muted)}
.pending-box em{font-style:normal;font-size:12px;color:var(--muted);opacity:.75}

.filegroup{margin:14px 0}
.filegroup h4,.hw h4{margin:0 0 8px;font-size:12px;text-transform:uppercase;
  letter-spacing:.08em;color:var(--muted)}
.files{display:flex;flex-wrap:wrap;gap:8px}
.files a{display:inline-flex;align-items:center;gap:8px;text-decoration:none;font-size:14px;
  padding:8px 13px;border-radius:9px;border:1px solid var(--line);background:var(--panel-2);
  transition:.15s}
.files a:hover{border-color:var(--accent);color:var(--accent)}
.files a.ext{border-style:dashed}
.ic{opacity:.6}
.notes .files a{background:var(--accent-soft);border-color:transparent;color:var(--accent)}

.hw{margin-top:14px;padding:14px 16px;background:var(--panel-2);border-radius:10px;
  border:1px solid var(--line)}
.hw ul{margin:0;padding-left:18px}
.hw li{margin:3px 0;font-size:14.5px}

/* school closure between two lessons */
.brk{display:flex;align-items:center;gap:14px;margin:20px 4px}
.brk::before,.brk::after{content:"";flex:1;height:1px;background:var(--line)}
.brk span{font-size:12px;text-transform:uppercase;letter-spacing:.09em;color:var(--muted);
  white-space:nowrap}

/* pagers */
.pagers{display:flex;gap:12px;margin-top:28px;flex-wrap:wrap}
.pager{flex:1;min-width:220px;display:flex;flex-direction:column;gap:2px;padding:14px 16px;
  border-radius:var(--radius);border:1px solid var(--line);background:var(--panel);
  text-decoration:none;box-shadow:var(--shadow)}
.pager:hover{border-color:var(--accent)}
.pager em{font-style:normal;font-size:12px;color:var(--muted)}
.pager.next{text-align:right}

.foot{max-width:940px;margin:0 auto;padding:20px;display:flex;justify-content:space-between;
  gap:12px;font-size:13px;color:var(--muted);border-top:1px solid var(--line)}
.linkish{background:none;border:0;color:var(--muted);cursor:pointer;font:inherit;
  text-decoration:underline;padding:0}
.linkish:hover{color:var(--accent)}