:root{
  --bg:#f6f7fb;--card:#fff;--ink:#17202f;--muted:#5d6779;--line:#e3e6ee;
  --pri:#4f46e5;--pri2:#7c3aed;--pri-ink:#fff;--ok:#0f9d58;--ok-bg:#e7f6ee;--no:#d93025;--no-bg:#fdecea;
  --warn:#b45309;--warn-bg:#fff4e0;--tip:#0e7490;--tip-bg:#e6f6f9;--chip:#eef0f7;--shadow:0 1px 2px rgba(20,30,60,.06),0 4px 16px rgba(20,30,60,.05);
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#0f1320;--card:#181d2c;--ink:#e8ebf3;--muted:#9aa3b5;--line:#2a3144;--pri:#8b84ff;--pri2:#b48cff;--pri-ink:#0f1320;
  --ok:#4ade80;--ok-bg:#12301f;--no:#f87171;--no-bg:#3a1717;--warn:#fbbf24;--warn-bg:#332611;--tip:#5fd4e8;--tip-bg:#102b31;--chip:#232a3d;--shadow:none}}
:root[data-theme="dark"]{--bg:#0f1320;--card:#181d2c;--ink:#e8ebf3;--muted:#9aa3b5;--line:#2a3144;--pri:#8b84ff;--pri2:#b48cff;--pri-ink:#0f1320;
  --ok:#4ade80;--ok-bg:#12301f;--no:#f87171;--no-bg:#3a1717;--warn:#fbbf24;--warn-bg:#332611;--tip:#5fd4e8;--tip-bg:#102b31;--chip:#232a3d;--shadow:none}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.6 system-ui,-apple-system,"Segoe UI",Roboto,sans-serif}
a{color:var(--pri)}
.top{position:sticky;top:0;z-index:5;display:flex;align-items:center;gap:20px;padding:10px 24px;background:var(--card);border-bottom:1px solid var(--line)}
.logo{font-weight:800;font-size:20px;text-decoration:none;color:var(--ink)}.logo span{color:var(--pri)}
.top nav{display:flex;gap:16px}.top nav a{text-decoration:none;color:var(--muted);font-weight:500}.top nav a:hover{color:var(--ink)}
.hstats{margin-left:auto;display:flex;gap:14px;font-size:14px;font-weight:600}
main{max-width:1080px;margin:0 auto;padding:24px 16px 48px}
.foot{text-align:center;color:var(--muted);font-size:13px;padding:24px 16px}
.card{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:20px;box-shadow:var(--shadow);margin-bottom:16px}
h1{font-size:30px;line-height:1.2;margin:4px 0 8px}h2.sec{margin:32px 0 12px}h3{margin:0 0 8px}h4{margin:8px 0 4px;font-size:17px}
.muted{color:var(--muted)}.small{font-size:14px}.center{text-align:center}
.eyebrow{text-transform:uppercase;letter-spacing:.08em;font-size:12px;font-weight:700;color:var(--pri);margin:0}
.lead{font-size:18px;color:var(--muted)}
.hero{display:grid;grid-template-columns:1.3fr 1fr;gap:24px;align-items:center;margin-bottom:16px}
.next{border:2px solid var(--pri)}
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}
.stat{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:14px;text-align:center}.stat b{display:block;font-size:24px}.stat span{font-size:13px;color:var(--muted)}
.level{margin-bottom:24px}.level-h{display:flex;gap:14px;align-items:center;margin-bottom:12px}.level-h p{margin:0}
.lvl{background:linear-gradient(135deg,var(--pri),var(--pri2));color:var(--pri-ink);font-weight:800;border-radius:10px;padding:8px 12px;white-space:nowrap}
.grid{display:grid;grid-template-columns:repeat(2,1fr);gap:14px}
.mod{display:flex;flex-direction:column;margin:0}.mod .row{margin-top:auto}.mod.locked{opacity:.6}
.mod-top{display:flex;justify-content:space-between;align-items:center}.ic{font-size:28px}.ic.big{font-size:44px}
.chip{display:inline-block;background:var(--chip);border-radius:999px;padding:2px 10px;font-size:12px;font-weight:600;margin-right:4px}
.chip.ok{background:var(--ok-bg);color:var(--ok)}.chip.warn{background:var(--warn-bg);color:var(--warn)}.chip.due{background:var(--tip-bg);color:var(--tip)}
.chip.learn{background:color-mix(in srgb,var(--pri) 15%,transparent);color:var(--pri)}.chip.ghost{background:transparent;border:1px solid var(--line)}
.bar{position:relative;height:8px;background:var(--chip);border-radius:99px;margin:10px 0 4px}.bar.lg{height:12px}
.bar>div{height:100%;border-radius:99px;background:linear-gradient(90deg,var(--pri),var(--pri2));transition:width .5s}
.bar>i{position:absolute;top:-3px;bottom:-3px;width:2px;background:var(--ok)}
.row{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin-top:10px}
.btn{font:inherit;font-weight:600;font-size:15px;border:1px solid var(--line);background:var(--card);color:var(--ink);border-radius:10px;padding:8px 16px;cursor:pointer;text-decoration:none;display:inline-block}
.btn:hover{border-color:var(--pri)}.btn:disabled{opacity:.5;cursor:default}
.btn.primary{background:var(--pri);border-color:var(--pri);color:var(--pri-ink)}.btn.primary.alt{background:var(--pri2);border-color:var(--pri2)}
.btn.small{padding:4px 10px;font-size:13px}.btn.link{border:0;background:none;color:var(--muted);text-decoration:underline}
.planned .plist{display:flex;flex-wrap:wrap;gap:8px}.plist span{border:1px dashed var(--line);border-radius:10px;padding:6px 12px;font-size:14px;color:var(--muted)}.plist em{font-size:12px}
.misc-card{border-left:4px solid var(--warn)}.misc-card li{margin:6px 0}
.back{text-decoration:none;font-size:14px}.mod-h{display:flex;gap:16px;align-items:center;margin:8px 0 16px}
.tabs{display:flex;gap:4px;border-bottom:1px solid var(--line);margin-bottom:16px;overflow-x:auto}
.tabs a{padding:10px 16px;text-decoration:none;color:var(--muted);font-weight:600;border-bottom:3px solid transparent;white-space:nowrap}.tabs a.on{color:var(--pri);border-color:var(--pri)}
.lesson h3{display:flex;align-items:center;gap:10px}.num{background:var(--pri);color:var(--pri-ink);width:26px;height:26px;border-radius:50%;display:inline-grid;place-items:center;font-size:14px;flex:none}
table{border-collapse:collapse;width:100%;margin:10px 0;font-size:15px}th,td{border-bottom:1px solid var(--line);padding:6px 10px;text-align:left}th{color:var(--muted);font-weight:600;font-size:13px}
code{background:var(--chip);padding:1px 6px;border-radius:5px}
.formula{background:var(--chip);border-left:4px solid var(--pri);padding:12px 16px;border-radius:8px;margin:12px 0;font-weight:500}
.callout{padding:12px 16px;border-radius:10px;margin:12px 0}.callout.misc{background:var(--warn-bg)}.callout.tip{background:var(--tip-bg)}
.callout.hook{background:linear-gradient(135deg,color-mix(in srgb,var(--pri) 12%,var(--card)),color-mix(in srgb,var(--pri2) 12%,var(--card)));border:1px solid var(--line)}
.flow{display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:8px;margin:14px 0}
.flow span{background:var(--pri);color:var(--pri-ink);padding:8px 14px;border-radius:10px;font-weight:700}.flow em{font-style:normal;font-size:13px;color:var(--muted);text-align:center}
.example .q{font-weight:600}.steps li{margin:6px 0}.steps li.hid{display:none}
.widget{display:grid;grid-template-columns:1fr 1fr;gap:16px;align-items:center;background:var(--chip);border-radius:12px;padding:16px}
.sliders label{display:grid;grid-template-columns:70px 1fr 44px;align-items:center;gap:8px;font-size:14px;margin:8px 0}
.gauge{text-align:center}.gauge p{margin:8px 0 0}.gauge b{font-size:20px;color:var(--pri)}
.box{position:relative;margin:0 auto;border:3px solid var(--ink);border-radius:6px;transition:width .3s,height .3s;overflow:hidden;--spd:2s}
.box i{position:absolute;width:8px;height:8px;border-radius:50%;background:var(--pri);animation:jit var(--spd) infinite alternate ease-in-out}
@keyframes jit{0%{transform:translate(0,0)}25%{transform:translate(18px,-14px)}50%{transform:translate(-12px,16px)}75%{transform:translate(14px,10px)}100%{transform:translate(-16px,-12px)}}
.qtop{display:flex;align-items:center;gap:14px;margin-bottom:16px}.qtop a{text-decoration:none;font-weight:600}
.pbar{flex:1;height:8px;background:var(--chip);border-radius:99px;overflow:hidden}.pbar div{height:100%;background:var(--ok);transition:width .4s}
.qgrid{display:grid;grid-template-columns:1fr 260px;gap:16px;align-items:start}
.qmeta{display:flex;flex-wrap:wrap;gap:4px;align-items:center;margin-bottom:12px}.diff{margin-left:auto;color:var(--pri);letter-spacing:2px}
.stem{font-size:19px;margin-bottom:16px}
.choices{display:grid;gap:8px}
.choice{display:flex;gap:12px;align-items:center;text-align:left;font:inherit;background:var(--card);color:var(--ink);border:2px solid var(--line);border-radius:12px;padding:12px 14px;cursor:pointer}
.choice span{flex:none;width:28px;height:28px;border-radius:50%;background:var(--chip);display:grid;place-items:center;font-weight:700;font-size:14px}
.choice:hover:not(:disabled){border-color:var(--pri)}.choice.sel{border-color:var(--pri);background:color-mix(in srgb,var(--pri) 8%,var(--card))}
.choice.right{border-color:var(--ok);background:var(--ok-bg)}.choice.wrong{border-color:var(--no);background:var(--no-bg)}.choice:disabled{cursor:default}
.numrow{display:flex;gap:10px;align-items:center}.numrow input{font:inherit;font-size:20px;padding:10px 14px;border:2px solid var(--line);border-radius:10px;width:240px;max-width:100%;background:var(--card);color:var(--ink)}
.numrow input:focus{outline:none;border-color:var(--pri)}.unit{font-weight:600;color:var(--muted)}
.actions{display:flex;justify-content:space-between;align-items:flex-end;gap:12px;flex-wrap:wrap;margin-top:18px}
.conf{text-align:right}.conf>div{display:flex;gap:6px;flex-wrap:wrap;justify-content:flex-end;margin-top:4px}
.feedback{margin-top:18px;border-radius:12px;padding:16px}.feedback.ok{background:var(--ok-bg)}.feedback.no{background:var(--no-bg)}
.feedback.ok h3{color:var(--ok)}.feedback.no h3{color:var(--no)}.feedback details{margin:8px 0}.feedback summary{cursor:pointer;font-weight:600}
.warn-t{color:var(--warn);font-weight:600}
.banner{padding:12px 14px;border-radius:10px;margin:10px 0}.banner.ok{background:var(--ok-bg);border:1px solid var(--ok)}.banner.warn{background:var(--warn-bg);border:1px solid var(--warn)}
.side{position:sticky;top:76px}
.summary{max-width:720px;margin:0 auto}.prose{max-width:780px;margin:0 auto}
.toast{position:fixed;left:50%;bottom:24px;transform:translate(-50%,20px);opacity:0;background:var(--ink);color:var(--bg);padding:10px 18px;border-radius:10px;transition:.25s;z-index:10;font-weight:600}
.toast.show{opacity:1;transform:translate(-50%,0)}
@media (max-width:760px){
  .top{flex-wrap:wrap;gap:10px;padding:10px 16px}.hstats{margin-left:0;width:100%}
  .hero,.grid,.qgrid,.widget{grid-template-columns:1fr}.stats{grid-template-columns:repeat(2,1fr)}
  h1{font-size:24px}.side{position:static}.conf{text-align:left}.conf>div{justify-content:flex-start}
}