:root{
  --bg:#f6f5f1; --surface:#ffffff; --surface-2:#f0eee8; --ink:#1b1d24; --ink-2:#4a4e5a; --muted:#7a7e8a;
  --line:#d6d2c6; --track:#d9d5ca; --accent:#2346a8; --accent-ink:#ffffff; --accent-soft:#e3e9f9; --accent-2:#b4352b;
  --ok:#1f7a4d; --ok-soft:#e1f3e9; --bad:#b4352b; --bad-soft:#fae6e3; --warn-soft:#fbf1d9; --warn:#8a5a00;
  --shadow:0 1px 2px rgba(20,22,30,.06),0 4px 16px rgba(20,22,30,.06);
  --r:14px; --head:"Bricolage Grotesque",system-ui,sans-serif; --body:"Atkinson Hyperlegible",system-ui,sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){
  :root:not([data-theme="light"]){
    --bg:#121419; --surface:#1b1e25; --surface-2:#232731; --ink:#eef0f5; --ink-2:#c3c7d2; --muted:#8b90a0;
    --line:#2e323d; --track:#3a3f4c; --accent:#8eaaff; --accent-ink:#0f1320; --accent-soft:#232c48; --accent-2:#ff8a7e;
    --ok:#5fd39a; --ok-soft:#173527; --bad:#ff8a7e; --bad-soft:#3d1f1d; --warn-soft:#3a2f14; --warn:#f2c46b;
    --shadow:0 1px 2px rgba(0,0,0,.3),0 4px 16px rgba(0,0,0,.25); color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --bg:#121419; --surface:#1b1e25; --surface-2:#232731; --ink:#eef0f5; --ink-2:#c3c7d2; --muted:#8b90a0;
  --line:#2e323d; --track:#3a3f4c; --accent:#8eaaff; --accent-ink:#0f1320; --accent-soft:#232c48; --accent-2:#ff8a7e;
  --ok:#5fd39a; --ok-soft:#173527; --bad:#ff8a7e; --bad-soft:#3d1f1d; --warn-soft:#3a2f14; --warn:#f2c46b;
  --shadow:0 1px 2px rgba(0,0,0,.3),0 4px 16px rgba(0,0,0,.25); color-scheme:dark;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:17px/1.55 var(--body);overflow-x:hidden}
a{color:var(--accent)}
h1,h2,h3{font-family:var(--head);line-height:1.15;margin:0 0 .4em;letter-spacing:-.01em}
h1{font-size:clamp(1.7rem,4vw,2.4rem);font-weight:700}
h2{font-size:1.35rem;font-weight:650}
h3{font-size:1.08rem;font-weight:650}
button{font:inherit;color:inherit}
.wrap{max-width:980px;margin:0 auto;padding:0 16px}

/* top bar */
.top{position:sticky;top:0;z-index:5;background:color-mix(in srgb,var(--bg) 88%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.top .wrap{display:flex;align-items:center;gap:12px;min-height:58px;flex-wrap:wrap;padding-top:6px;padding-bottom:6px}
.brand{font-family:var(--head);font-weight:700;font-size:1.05rem;text-decoration:none;color:var(--ink);display:flex;align-items:center;gap:8px;white-space:nowrap}
.brand .dot{width:26px;height:26px;border-radius:8px;background:var(--accent);color:var(--accent-ink);display:grid;place-items:center;font-size:.8rem}
nav.tabs{display:flex;gap:4px;flex-wrap:wrap;margin-left:auto}
nav.tabs a{padding:7px 12px;border-radius:999px;text-decoration:none;color:var(--ink-2);font-size:.95rem}
nav.tabs a:hover{background:var(--surface-2)}
nav.tabs a.on{background:var(--accent);color:var(--accent-ink)}
nav.tabs .s{display:none}
.sel{font:inherit;font-size:.95rem;color:var(--ink);background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:8px 10px;max-width:100%}
.icon-btn{border:1px solid var(--line);background:var(--surface);border-radius:999px;width:36px;height:36px;cursor:pointer;display:grid;place-items:center}

main{padding:22px 0 60px}
.back{display:inline-block;margin-bottom:12px;color:var(--muted);text-decoration:none;font-size:.95rem}
.back:hover{color:var(--accent)}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);box-shadow:var(--shadow);padding:20px}
.grid{display:grid;gap:14px;grid-template-columns:repeat(auto-fill,minmax(260px,1fr))}
.muted{color:var(--muted)}
.small{font-size:.9rem}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.spacer{flex:1}

.btn{display:inline-flex;align-items:center;gap:8px;border:1px solid var(--line);background:var(--surface);border-radius:10px;padding:9px 16px;cursor:pointer;text-decoration:none;color:var(--ink);font-weight:600;font-size:.98rem}
.btn:hover{border-color:var(--accent)}
.btn.primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.btn.primary:hover{filter:brightness(1.08)}
.btn.ghost{background:transparent}
.btn:disabled{opacity:.45;cursor:not-allowed}
.btn.sm{padding:6px 12px;font-size:.9rem}
kbd{font-family:ui-monospace,monospace;font-size:.75em;border:1px solid var(--line);border-bottom-width:2px;border-radius:5px;padding:0 5px;color:var(--muted);background:var(--surface)}

/* hero */
.hero{display:grid;grid-template-columns:1.4fr 1fr;gap:16px;margin-bottom:22px}
.hero .lead{font-size:1.08rem;color:var(--ink-2);margin:0}
.examchip{display:inline-flex;align-items:center;gap:8px;background:var(--accent-soft);color:var(--accent);padding:5px 12px;border-radius:999px;font-weight:700;font-size:.9rem;margin-bottom:12px}
.steps{margin:0;padding-left:1.2em}
.steps li{margin:.25em 0}
.stat{font-family:var(--head);font-size:2.2rem;font-weight:700;line-height:1}
.bar{height:8px;border-radius:999px;background:var(--track);overflow:hidden}
.bar>i{display:block;height:100%;background:var(--accent);border-radius:999px;transition:width .3s}
.bar.ok>i{background:var(--ok)}

/* unit cards */
.unit{display:flex;flex-direction:column;gap:10px}
.unit .num{font-family:var(--head);font-size:.85rem;color:var(--muted);font-weight:600}
.unit h3{margin:0}
.unit .meta{font-size:.88rem;color:var(--muted)}
.unit .row{margin-top:auto}
.pill{display:inline-block;font-size:.78rem;padding:2px 9px;border-radius:999px;background:var(--surface-2);color:var(--ink-2);font-weight:600}
.pill.ok{background:var(--ok-soft);color:var(--ok)}
.pill.warn{background:var(--warn-soft);color:var(--warn)}

/* learn */
.learn-head{margin-bottom:16px}
.bigidea{background:var(--accent-soft);border-left:4px solid var(--accent);border-radius:10px;padding:14px 16px;font-size:1.08rem;margin:0 0 18px}
.points{margin:0;padding-left:1.15em}
.points li{margin:0 0 .75em}
.section{margin-top:22px}
.terms{display:grid;grid-template-columns:repeat(auto-fill,minmax(270px,1fr));gap:10px}
.term{background:var(--surface-2);border-radius:10px;padding:10px 12px}
.term b{display:block;font-family:var(--head);font-weight:650}
.term span{font-size:.93rem;color:var(--ink-2)}
table.cases{width:100%;border-collapse:collapse;font-size:.95rem}
table.cases th,table.cases td{text-align:left;padding:8px 10px;border-bottom:1px solid var(--line);vertical-align:top}
table.cases th{font-family:var(--head);font-weight:650;color:var(--muted);font-size:.85rem}
table.cases td:nth-child(2){white-space:nowrap;color:var(--muted)}
details.more{margin-top:14px;border-top:1px solid var(--line);padding-top:10px}
details.more summary{cursor:pointer;font-weight:700;color:var(--accent);padding:4px 0}
details.more[open] summary{margin-bottom:6px}
.traps{background:var(--warn-soft);border-radius:10px;padding:12px 16px}
.traps ul{margin:.3em 0 0;padding-left:1.1em}
.traps h3{color:var(--warn)}
.pager{display:flex;justify-content:space-between;gap:10px;margin-top:26px;flex-wrap:wrap}

/* chips */
.chips{display:flex;flex-wrap:wrap;gap:8px}
.chip{border:1px solid var(--line);background:var(--surface);border-radius:999px;padding:6px 12px;cursor:pointer;font-size:.92rem}
.chip.on{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}

/* flashcards */
.flash-wrap{max-width:640px;margin:0 auto}
.flash{perspective:1400px;cursor:pointer;margin:14px 0}
.flash .inner{position:relative;min-height:260px;transition:transform .45s;transform-style:preserve-3d}
.flash.flipped .inner{transform:rotateY(180deg)}
.flash .face{position:absolute;inset:0;backface-visibility:hidden;-webkit-backface-visibility:hidden;background:var(--surface);border:1px solid var(--line);border-radius:18px;box-shadow:var(--shadow);display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center;padding:26px}
.flash .back-face{transform:rotateY(180deg);background:var(--accent-soft)}
.flash .face .lbl{position:absolute;top:12px;left:16px;font-size:.78rem;color:var(--muted);font-weight:600;text-transform:uppercase;letter-spacing:.05em}
.flash .front-txt{font-family:var(--head);font-size:clamp(1.3rem,3.6vw,1.8rem);font-weight:650}
.flash .back-txt{font-size:1.1rem}
.flash-ctrl{display:flex;gap:10px;justify-content:center;flex-wrap:wrap}

/* quiz */
.qwrap{max-width:720px;margin:0 auto}
.qhead{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-bottom:10px;flex-wrap:wrap}
.qtext{font-size:1.18rem;font-weight:600;margin:6px 0 16px;font-family:var(--head)}
.opts{display:grid;gap:10px}
.opt{display:flex;gap:12px;align-items:flex-start;text-align:left;width:100%;border:1.5px solid var(--line);background:var(--surface);border-radius:12px;padding:12px 14px;cursor:pointer;font-size:1rem}
.opt:hover:not(:disabled){border-color:var(--accent)}
.opt .k{flex:0 0 26px;height:26px;border-radius:7px;background:var(--surface-2);display:grid;place-items:center;font-weight:700;font-size:.85rem;color:var(--ink-2)}
.opt.sel{border-color:var(--accent);background:var(--accent-soft)}
.opt.right{border-color:var(--ok);background:var(--ok-soft)}
.opt.right .k{background:var(--ok);color:#fff}
.opt.wrong{border-color:var(--bad);background:var(--bad-soft)}
.opt.wrong .k{background:var(--bad);color:#fff}
.opt:disabled{cursor:default}
.explain{margin-top:14px;border-radius:12px;padding:12px 14px;background:var(--surface-2)}
.explain.ok{background:var(--ok-soft)}
.explain.bad{background:var(--bad-soft)}
.explain b{font-family:var(--head)}
.result-big{font-family:var(--head);font-size:3rem;font-weight:700;line-height:1}
.review-item{border-top:1px solid var(--line);padding:12px 0}
.review-item:first-child{border-top:0}
.tag{font-size:.75rem;color:var(--muted);font-weight:600;text-transform:uppercase;letter-spacing:.04em}

/* writing */
textarea{width:100%;min-height:190px;font:inherit;font-size:1rem;color:var(--ink);background:var(--surface);border:1.5px solid var(--line);border-radius:12px;padding:12px 14px;resize:vertical}
textarea:focus{outline:none;border-color:var(--accent)}
.checklist{list-style:none;padding:0;margin:8px 0 0;display:grid;gap:8px}
.checklist label{display:flex;gap:10px;align-items:flex-start;background:var(--surface-2);border-radius:10px;padding:9px 12px;cursor:pointer}
.checklist input{margin-top:5px;width:18px;height:18px;accent-color:var(--ok)}
.checklist .auto{font-size:.75rem;color:var(--ok);font-weight:700;margin-left:6px}
.model{background:var(--accent-soft);border-radius:12px;padding:14px 16px;white-space:pre-wrap}
textarea.essay{min-height:360px}
.opts.tf{grid-template-columns:1fr 1fr}
.sa-list .sa-item{display:flex;gap:12px;align-items:flex-start;padding:12px 0;border-top:1px solid var(--line);text-decoration:none;color:var(--ink)}
.sa-list .sa-item:hover .q{color:var(--accent)}
.sa-list h3{margin-top:20px}
.tip{background:var(--surface-2);border-radius:10px;padding:10px 14px;font-size:.95rem}

/* exam */
.exam-q{padding:16px 0;border-top:1px solid var(--line)}
.exam-q:first-of-type{border-top:0}
.exam-q .opts{gap:8px}
.timer{font-family:ui-monospace,monospace;font-weight:700;background:var(--surface-2);padding:4px 10px;border-radius:8px}
.sticky-foot{position:sticky;bottom:0;background:color-mix(in srgb,var(--bg) 92%,transparent);backdrop-filter:blur(6px);border-top:1px solid var(--line);padding:10px 0;margin-top:20px}

.empty{text-align:center;padding:40px 10px}
.foot{color:var(--muted);font-size:.85rem;text-align:center;padding:30px 0}

@media (max-width:760px){
  body{font-size:16px}
  .hero{grid-template-columns:1fr}
  nav.tabs{margin-left:0;width:100%;order:3;justify-content:space-between;gap:2px}
  nav.tabs a{padding:6px 10px;font-size:.92rem}
  nav.tabs .l{display:none}
  nav.tabs .s{display:inline}
  .icon-btn{margin-left:auto}
  .card{padding:16px}
  .flash .inner{min-height:300px}
  table.cases td:nth-child(2){white-space:normal}
}
@media print{.top,.pager,.btn{display:none}}