/* Shared styles for the lesson pages (tutor.html, study.html). */
:root{
  --bg:#f6f5f1; --surface:#ffffff; --sunk:#ecebe5; --ink:#1a1a1a; --muted:#5c5b57; --rule:#dad8d0;
  --accent:#1d4e89; --accent-ink:#ffffff; --accent-soft:#dfe8f3;
  --curve:#1d4e89; --base:#9e9c95; --asym:#d0422f; --grid:#e6e4dd; --axis:#5f5e59;
  --hl:#ffe98a; --hl-ink:#3b3100;
  --good:#17744a; --good-soft:#dcf1e5; --bad:#b3261e; --bad-soft:#f8e0de; --warn-soft:#fbf0d2; --warn:#8a5a00;
  --display:"Source Serif 4","Segoe UI",system-ui,sans-serif;
  --body:"IBM Plex Sans","Segoe UI",system-ui,sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,Consolas,monospace;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    color-scheme:dark;
    --bg:#141516; --surface:#1b1c1e; --sunk:#232427; --ink:#e8e6e1; --muted:#a3a19b; --rule:#323338;
    --accent:#8fb3e0; --accent-ink:#0e1621; --accent-soft:#1c2a3d;
    --curve:#9dbde6; --base:#6f6e6a; --asym:#ff7a66; --grid:#2a2b2e; --axis:#9d9b95;
    --hl:#5c4d12; --hl-ink:#fff3c2;
    --good:#5fd39a; --good-soft:#123527; --bad:#ff8a80; --bad-soft:#3d1a18; --warn-soft:#3a2f12; --warn:#f3c969;
  }
}
:root[data-theme="dark"]{
  color-scheme:dark;
  --bg:#141516; --surface:#1b1c1e; --sunk:#232427; --ink:#e8e6e1; --muted:#a3a19b; --rule:#323338;
  --accent:#8fb3e0; --accent-ink:#0e1621; --accent-soft:#1c2a3d;
  --curve:#9dbde6; --base:#6f6e6a; --asym:#ff7a66; --grid:#2a2b2e; --axis:#9d9b95;
  --hl:#5c4d12; --hl-ink:#fff3c2;
  --good:#5fd39a; --good-soft:#123527; --bad:#ff8a80; --bad-soft:#3d1a18; --warn-soft:#3a2f12; --warn:#f3c969;
}
*{box-sizing:border-box}
body{background:var(--bg);color:var(--ink);font-family:var(--body);font-size:18px;line-height:1.6;padding-inline:16px;padding-block:0 96px}
a{color:var(--accent)}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px;border-radius:4px}
@media (prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}
button{font:inherit;color:inherit}
sup,sub{line-height:0}

.app{max-width:1400px;margin:0 auto;display:grid;grid-template-columns:250px minmax(0,1fr) 360px;gap:32px;align-items:start}
@media (max-width:1250px){.app{grid-template-columns:230px minmax(0,1fr)}}
@media (max-width:860px){.app{grid-template-columns:minmax(0,1fr);gap:0}}

.map{position:sticky;top:env(safe-area-inset-top,0px);padding-block:24px;max-height:100vh;overflow:auto}
.brand{font-family:var(--display);font-weight:700;font-size:20px;line-height:1.1;margin-bottom:4px}
.brand-sub{font-size:13px;color:var(--muted);margin-bottom:16px}
.overall{font-family:var(--mono);font-size:12px;color:var(--muted)}
.bar{height:6px;border-radius:3px;background:var(--sunk);overflow:hidden;margin:6px 0 18px}
.bar>i{display:block;height:100%;background:var(--good);width:0;transition:width .3s}
.map ol{list-style:none;margin:0;padding:0;display:grid;gap:1px}
.map li button{width:100%;text-align:left;background:none;border:0;border-radius:8px;padding:6px 8px;cursor:pointer;display:flex;gap:10px;align-items:center;font-size:14.5px;line-height:1.3}
.map li button:hover{background:var(--surface)}
.map li button[aria-current="true"]{background:var(--accent-soft);font-weight:700}
.dot{flex:none;width:22px;height:22px;border-radius:50%;border:2px solid var(--rule);display:grid;place-items:center;font-family:var(--mono);font-size:10.5px;color:var(--muted)}
.done .dot{background:var(--good);border-color:var(--good);color:var(--bg)}
.map .part{font-family:var(--mono);font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);padding:12px 8px 4px}
.qtag{font-family:var(--mono);font-size:10.5px;color:var(--muted);margin-left:auto;white-space:nowrap}
.map-toggle{display:none}
@media (max-width:860px){
  .map{position:static;max-height:none;padding-block:14px 0}
  .map-toggle{display:flex;width:100%;justify-content:space-between;align-items:center;background:var(--surface);border:1px solid var(--rule);border-radius:6px;padding:10px 14px;cursor:pointer;font-weight:700}
  .map-body{margin-top:10px}
  .map-body.closed{display:none}
  .brand,.brand-sub{display:none}
}

.lesson{padding-block:24px;min-width:0}
.crumb{font-family:var(--mono);font-size:12.5px;color:var(--muted);display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}
.unit-title{font-family:var(--display);font-weight:700;font-size:clamp(26px,4vw,38px);line-height:1.08;letter-spacing:-.01em;margin:6px 0 14px;text-wrap:balance}
.ubar{display:flex;gap:3px;margin-bottom:22px}
.ubar i{flex:1;height:5px;border-radius:3px;background:var(--sunk)}
.ubar i.on{background:var(--accent)}
.ubar i.cur{background:var(--ink)}
.card{background:var(--surface);border:1px solid var(--rule);border-radius:8px;padding:26px 28px;max-width:760px}
@media (max-width:560px){.card{padding:20px 18px}}
.kind{display:inline-block;font-family:var(--mono);font-size:11px;letter-spacing:.07em;text-transform:uppercase;padding:3px 9px;border-radius:999px;margin-bottom:10px}
.kind.learn{background:var(--accent-soft);color:var(--accent)}
.kind.ex{background:var(--warn-soft);color:var(--warn)}
.kind.check{background:var(--good-soft);color:var(--good)}
.kind.review{background:var(--sunk);color:var(--muted)}
.setup{font-size:17px;line-height:1.55;margin-bottom:12px}
.setup .fx{font-family:var(--mono,inherit);font-size:21px;margin:10px 0 2px;padding:10px 14px;background:var(--sunk);border-radius:6px;display:inline-block}
.ask{font-size:18px;margin:6px 0 4px}
.partno{display:inline-block;font-size:12px;font-weight:700;letter-spacing:.04em;text-transform:uppercase;color:var(--accent);margin-right:6px}
details.worked{margin-top:10px;font-size:15px}details.worked summary{cursor:pointer;font-weight:600}
details.worked ol{margin:8px 0 0 20px}details.worked .why{display:block;color:var(--muted);font-size:13px}
.score-big{font-size:44px;font-weight:700;margin:6px 0}
.score-list{list-style:none;padding:0;columns:2;font-size:15px}.score-list li{padding:3px 0;break-inside:avoid}
.score-list .y{color:var(--good)}.score-list .n{color:var(--bad,#d0422f)}
.card h2{font-family:var(--display);font-size:25px;line-height:1.2;margin:0 0 12px;text-wrap:balance}
.card p{margin:0 0 14px}
.card ul,.card ol{margin:0 0 14px;padding-left:24px}
.card li{margin-bottom:6px}
.big{font-size:20px}
.key{background:var(--hl);color:var(--hl-ink);padding:0 .25em;border-radius:3px}
.box{background:var(--sunk);border-radius:6px;padding:14px 16px;margin:0 0 14px}
.box > :last-child{margin-bottom:0}
.analogy{border-left:4px solid var(--accent);padding:6px 0 6px 14px;margin:0 0 14px}
.analogy b:first-child{color:var(--accent)}
.examq{border:1.5px dashed var(--accent);border-radius:6px;padding:10px 14px;margin:0 0 14px;font-size:16.5px}
.examq b:first-child{font-family:var(--mono);font-size:11.5px;letter-spacing:.06em;text-transform:uppercase;color:var(--accent);display:block}
table{border-collapse:collapse;font-size:16px;margin:0 0 14px;min-width:100%}
.tw{overflow-x:auto}
th,td{text-align:left;padding:6px 10px;border-bottom:1px solid var(--rule)}
th{font-family:var(--display);font-size:13px;text-transform:uppercase;letter-spacing:.04em;color:var(--muted)}
.m{font-family:var(--mono);font-size:.92em}
.work{font-family:var(--mono);font-size:15.5px;background:var(--sunk);border-radius:6px;padding:12px 14px;margin:0 0 14px;overflow-x:auto;line-height:2;white-space:pre}
.f{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;line-height:1.35;margin:0 3px}
.f>span:first-child{border-bottom:1.5px solid currentColor;padding:0 4px}
.f>span:last-child{padding:0 4px}
.plot{margin:4px 0 14px;max-width:420px}
.plot svg{width:100%;height:auto;display:block;background:var(--surface);border:1px solid var(--rule);border-radius:6px}
.plot-legend{display:flex;flex-wrap:wrap;gap:4px 14px;font-size:13px;color:var(--muted);margin-top:4px}
.plot-legend i{display:inline-block;width:18px;height:0;border-top:3px solid;vertical-align:middle;margin-right:5px}

.steps{list-style:none;padding:0;margin:0 0 14px;display:grid;gap:10px;counter-reset:st}
.steps li{border:1px solid var(--rule);border-radius:6px;padding:12px 14px 12px 50px;position:relative;counter-increment:st;animation:pop .25s ease;min-width:0}
.steps li::before{content:counter(st);position:absolute;left:14px;top:12px;width:24px;height:24px;border-radius:50%;background:var(--ink);color:var(--bg);font-family:var(--mono);font-size:12px;display:grid;place-items:center}
.steps .why{display:block;color:var(--muted);font-size:15.5px;margin-top:4px}
.steps .work{margin:8px 0 2px}
@keyframes pop{from{opacity:.3;transform:translateY(4px)}to{opacity:1;transform:none}}

.q{font-size:19px;margin-bottom:14px}
.choices{display:grid;gap:8px;margin-bottom:12px}
.fsheet{border:1px solid var(--rule);border-radius:6px;padding:10px 14px 12px;margin:0 0 16px;background:var(--sunk)}
.fsheet .fs-h{font:700 12px/1.3 var(--mono);letter-spacing:.05em;text-transform:uppercase;color:var(--muted);margin-bottom:8px}
.fsheet .fs-h span{text-transform:none;letter-spacing:0;font-weight:400}
.fsheet .fs-g{display:grid;grid-template-columns:repeat(auto-fit,minmax(170px,1fr));gap:8px 18px;align-items:center}
.fsheet .m{font-size:19px;font-family:"Cambria Math","Cambria","Times New Roman",serif;font-style:italic;white-space:nowrap}
.fsheet .paren{font-size:1.5em;vertical-align:-.12em;font-style:normal;margin:0 2px}
.redeem-bar{display:flex;gap:14px;align-items:center;justify-content:space-between;background:var(--warn-soft);border-radius:6px;padding:10px 14px;margin:-6px 0 16px;font-size:15px}
.redeem-bar .dots{display:flex;gap:6px;flex:none}
.redeem-bar .dots i{width:14px;height:14px;border-radius:50%;border:2px solid var(--warn);display:block}
.redeem-bar .dots i.on{background:var(--good);border-color:var(--good)}
.choice{text-align:left;border:1.5px solid var(--rule);background:var(--bg);border-radius:6px;padding:10px 14px;cursor:pointer;font-size:17px;display:flex;gap:12px;align-items:baseline}
.choice .l{font-family:var(--mono);font-size:13px;color:var(--muted)}
.choice:hover:not(:disabled){border-color:var(--accent)}
.choice:disabled{cursor:default}
.choice.right{background:var(--good-soft);border-color:var(--good)}
.choice.wrong{background:var(--bad-soft);border-color:var(--bad)}
.choice.dim{opacity:.55}
.answer-row{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin-bottom:8px}
.answer-row input{flex:1;min-width:180px;font-family:var(--mono);font-size:17px;padding:10px 12px;border-radius:6px;border:1.5px solid var(--rule);background:var(--bg);color:var(--ink)}
.answer-row input:focus{border-color:var(--accent);outline:none}
.unit-lbl{font-family:var(--mono);color:var(--muted);font-size:15px}
.fmt{font-size:13.5px;color:var(--muted);margin:0 0 12px}
.preview{font-family:var(--mono);font-size:13.5px;color:var(--muted);margin:-2px 0 10px;min-height:1.2em}
.fb{border-radius:6px;padding:12px 14px;margin-bottom:12px;font-size:16.5px}
.fb.ok{background:var(--good-soft)}
.fb.ok b:first-child{color:var(--good)}
.fb.no{background:var(--bad-soft)}
.fb.no b:first-child{color:var(--bad)}
.fb.hint{background:var(--warn-soft)}
.fb.hint b:first-child{color:var(--warn)}

.nav{display:flex;gap:10px;flex-wrap:wrap;align-items:center;margin-top:18px;max-width:760px}
.btn{font-family:var(--body);font-size:16px;font-weight:700;border-radius:6px;padding:10px 18px;border:1.5px solid var(--rule);background:var(--surface);cursor:pointer}
.btn:hover:not(:disabled){border-color:var(--accent)}
.btn:disabled{opacity:.45;cursor:default}
.btn.primary{background:var(--accent);color:var(--accent-ink);border-color:var(--accent)}
.btn.ghost{background:none;border-color:transparent;color:var(--muted);font-weight:400;padding-inline:8px}
.btn.ghost:hover{color:var(--accent)}
.spacer{flex:1}
.kbd{font-family:var(--mono);font-size:12px;color:var(--muted)}

.tutor{position:sticky;top:env(safe-area-inset-top,0px);padding-block:24px;height:100vh;display:flex;flex-direction:column;min-height:0}
.tutor-inner{background:var(--surface);border:1px solid var(--rule);border-radius:8px;display:flex;flex-direction:column;min-height:0;flex:1;overflow:hidden}
.t-head{padding:14px 16px 10px;border-bottom:1px solid var(--rule)}
.t-head h3{font-family:var(--display);font-size:18px;margin:0;display:flex;justify-content:space-between;align-items:center}
.t-head p{margin:2px 0 0;font-size:13.5px;color:var(--muted)}
.t-quick{display:flex;flex-wrap:wrap;gap:6px;padding:10px 16px;border-bottom:1px solid var(--rule)}
.chip{border:1px solid var(--rule);background:var(--bg);border-radius:999px;padding:5px 11px;font-size:13.5px;cursor:pointer}
.chip:hover:not(:disabled){border-color:var(--accent)}
.chip:disabled{opacity:.5;cursor:default}
.t-log{flex:1;overflow:auto;padding:14px 16px;display:flex;flex-direction:column;gap:10px;font-size:15.5px;min-height:120px}
.msg{padding:9px 12px;border-radius:6px;white-space:pre-wrap;line-height:1.5;max-width:95%}
.msg.me{background:var(--accent);color:var(--accent-ink);align-self:flex-end;border-bottom-right-radius:4px}
.msg.ai{background:var(--sunk);align-self:flex-start;border-bottom-left-radius:4px}
.msg.sys{color:var(--muted);font-size:13.5px;align-self:center;text-align:center;white-space:normal}
.t-form{display:flex;gap:6px;padding:10px 12px;border-top:1px solid var(--rule)}
.t-form textarea{flex:1;resize:none;font:inherit;font-size:15px;padding:8px 10px;border-radius:6px;border:1px solid var(--rule);background:var(--bg);color:var(--ink);min-height:42px;max-height:120px}
.t-close{display:none;background:none;border:0;font-size:22px;cursor:pointer;color:var(--muted);line-height:1}
.fab{display:none}
@media (max-width:1250px){
  .tutor{position:fixed;inset:auto 0 0 0;height:min(78vh,640px);padding:0 8px calc(8px + env(safe-area-inset-bottom,0px));z-index:10;transform:translateY(105%);transition:transform .25s}
  .tutor.open{transform:none}
  .tutor-inner{box-shadow:0 -8px 30px rgba(0,0,0,.18)}
  .t-close{display:block}
  .fab{display:flex;position:fixed;right:16px;bottom:calc(16px + env(safe-area-inset-bottom,0px));z-index:9;align-items:center;gap:8px;background:var(--ink);color:var(--bg);border:0;border-radius:999px;padding:12px 18px;font-weight:700;cursor:pointer;box-shadow:0 6px 20px rgba(0,0,0,.2)}
}

/* lesson tags are internal (they map lessons to videos); students don't need to see them */
.qtag{display:none}