:root{--bg:#f5f6f8;--card:#fff;--ink:#1d2433;--mute:#677086;--line:#e2e5ec;--pri:#1f5fbf;--pri-ink:#fff;--ok:#1a8a4a;--okbg:#e3f5ea;--bad:#c23a3a;--badbg:#fbe6e6;--sel:#e6efff;--warn:#b7791f;--tip:#fff6dc}
@media(prefers-color-scheme:dark){:root{--bg:#121620;--card:#1b2130;--ink:#e8ebf2;--mute:#9aa3b8;--line:#2a3247;--pri:#5b94f0;--pri-ink:#0b1220;--ok:#4cc783;--okbg:#17352a;--bad:#ef7b7b;--badbg:#3a1f25;--sel:#1f2a44;--warn:#e0b45a;--tip:#3a331c}}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.6 system-ui,-apple-system,"Segoe UI",Tahoma,"Noto Naskh Arabic",sans-serif;padding-bottom:70px}
.wrap{max-width:860px;margin:0 auto;padding:16px}
h1{font-size:22px;margin:8px 0 4px}h2{font-size:18px;margin:18px 0 8px}h3{font-size:16px;margin:0 0 6px}
.mute{color:var(--mute);font-size:14px}
.card{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:14px;margin:10px 0}
.row{display:flex;gap:10px;align-items:center;flex-wrap:wrap}.sp{flex:1}
button{font:inherit;border:1px solid var(--line);background:var(--card);color:var(--ink);border-radius:10px;padding:9px 14px;cursor:pointer}
button:hover{border-color:var(--pri)}button.pri{background:var(--pri);color:var(--pri-ink);border-color:var(--pri)}
button:disabled{opacity:.45;cursor:not-allowed}.opt:disabled{opacity:1;cursor:default;color:var(--ink)}
.bar{height:8px;background:var(--line);border-radius:6px;overflow:hidden;margin-top:8px}.bar>i{display:block;height:100%;background:var(--pri)}
.lesson{cursor:pointer}.lesson:hover{border-color:var(--pri)}
.num{display:inline-block;min-width:30px;text-align:center;background:var(--sel);color:var(--pri);border-radius:8px;padding:1px 6px;font-weight:600;margin-inline-end:8px;direction:ltr}
.de{direction:ltr;text-align:left}
.badge{font-size:13px;padding:2px 8px;border-radius:20px;background:var(--sel);color:var(--pri);direction:ltr;display:inline-block}
.badge.ok{background:var(--okbg);color:var(--ok)}.badge.mid{background:#fff3d6;color:var(--warn)}.badge.bad{background:var(--badbg);color:var(--bad)}
.q{font-size:18px;font-weight:600;margin:6px 0 12px}
.opt{display:flex;gap:10px;align-items:flex-start;width:100%;text-align:left;direction:ltr;margin:8px 0;padding:11px 12px;border-radius:10px;border:2px solid var(--line);background:var(--card)}
.opt .k{flex:none;width:26px;height:26px;border-radius:7px;border:2px solid var(--line);display:flex;align-items:center;justify-content:center;font-size:13px;font-weight:700}
.opt.sel{border-color:var(--pri);background:var(--sel)}.opt.sel .k{background:var(--pri);color:var(--pri-ink);border-color:var(--pri)}
.opt.right{border-color:var(--ok);background:var(--okbg)}.opt.wrong{border-color:var(--bad);background:var(--badbg)}.opt.missed{border-style:dashed;border-color:var(--ok)}
.hint{background:var(--sel);border-radius:10px;padding:8px 12px;margin-bottom:10px;font-size:15px}
.expl{margin-top:12px;padding:10px 12px;border-radius:10px;background:var(--sel);direction:ltr;text-align:left}
.res{font-size:44px;font-weight:700;text-align:center;direction:ltr;margin:6px 0}
.crumb{font-size:14px;color:var(--mute);margin-bottom:6px;direction:ltr;text-align:left}
.top{display:flex;gap:8px;margin-bottom:6px}
.ar{direction:rtl;text-align:right;line-height:1.6;background:var(--sel);border-radius:10px;padding:8px 12px;margin:-4px 0 12px}
.aro{display:block;direction:rtl;text-align:right;font-size:15px;color:var(--mute);margin-top:6px;padding-top:6px;border-top:1px dashed var(--line)}
.expl .ar2{display:block;direction:rtl;text-align:right;margin-top:8px;padding-top:8px;border-top:1px dashed var(--mute)}
.sp1{flex:1}a{color:var(--pri)}
/* nav */
#nav{position:fixed;inset:auto 0 0 0;display:flex;background:var(--card);border-top:1px solid var(--line);padding-bottom:env(safe-area-inset-bottom);z-index:5}
#nav button{flex:1;border:0;border-radius:0;background:none;padding:10px 4px;font-size:13px;color:var(--mute)}
#nav button b{display:block;font-size:20px;line-height:1}#nav button.on{color:var(--pri);font-weight:700}
/* study */
.sec{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:14px;margin:12px 0}
.sec h3{font-size:18px;color:var(--pri)}
.sec ul{margin:6px 0;padding:0 20px 0 0}.sec li{margin:5px 0}
.tip{background:var(--tip);border-inline-start:4px solid var(--warn);border-radius:8px;padding:8px 12px;margin:8px 0}
.formula{direction:ltr;text-align:left;font-family:ui-monospace,Menlo,Consolas,monospace;background:var(--sel);border-radius:8px;padding:8px 12px;margin:8px 0;overflow-x:auto;white-space:pre-wrap}
.case{background:var(--okbg);border-inline-start:4px solid var(--ok);border-radius:8px;padding:10px 12px;margin:10px 0}
.diagram{width:100%;border-radius:10px;border:1px solid var(--line);background:#fff;margin:8px 0}
.thumbs{display:flex;gap:8px;overflow-x:auto;padding:6px 0;direction:ltr}
.thumbs img{height:84px;border-radius:6px;border:1px solid var(--line);cursor:zoom-in;flex:none;background:#fff}
.scene3d{position:relative;height:min(62vh,420px);border-radius:12px;overflow:hidden;background:linear-gradient(#eef3fb,#d7e1f0);margin:8px 0;touch-action:none;direction:ltr}
.scene3d canvas{display:block;width:100%;height:100%}
.lbls{position:absolute;inset:0;pointer-events:none}
.lbl{position:absolute;transform:translate(-50%,-120%);font:600 11px/1.2 system-ui,sans-serif;background:rgba(15,39,64,.85);color:#fff;padding:3px 6px;border-radius:6px;white-space:nowrap}
.lbl.y{background:#b58100}.lbl.r{background:#b02a2a}.lbl.g{background:#1a7a42}.lbl.b{background:#1f5fbf}
.btn3d{position:absolute;left:8px;bottom:8px;font-size:13px;padding:6px 10px;z-index:2}
.note3d{position:absolute;left:8px;right:8px;top:8px;background:rgba(255,255,255,.92);color:#1d2433;font:13px/1.4 system-ui,sans-serif;padding:6px 10px;border-radius:8px;direction:ltr;text-align:left;z-index:2}
.note3d.bad{background:#fde7e7;color:#8f1d1d}
.hint3d{font-size:13px;color:var(--mute)}
.chips{display:flex;gap:8px;flex-wrap:wrap;margin:8px 0}.chip{padding:6px 12px;border-radius:20px;border:1px solid var(--line);background:var(--card);cursor:pointer;font-size:14px}
.chip.on{background:var(--pri);color:var(--pri-ink);border-color:var(--pri)}
.day{display:flex;gap:10px;align-items:flex-start}.day .d{flex:none;width:44px;height:44px;border-radius:12px;background:var(--sel);color:var(--pri);font-weight:700;display:flex;align-items:center;justify-content:center;direction:ltr}
.day.today{border-color:var(--pri);box-shadow:0 0 0 2px var(--pri) inset}.day.done .d{background:var(--ok);color:#fff}
/* lightbox */
#lb{position:fixed;inset:0;background:rgba(0,0,0,.92);z-index:20;display:flex;align-items:center;justify-content:center;direction:ltr}
#lb[hidden]{display:none}#lb img{max-width:100%;max-height:88vh;background:#fff}
#lb button{position:absolute;background:rgba(255,255,255,.15);color:#fff;border:0;font-size:28px;width:48px;height:48px;border-radius:24px;padding:0}
#lb .x{top:10px;right:10px}#lb .pv{left:8px;top:50%}#lb .nx{right:8px;top:50%}
#lb .cap{position:absolute;bottom:12px;left:0;right:0;text-align:center;color:#fff;font-size:14px}

.pt{border-inline-start:3px solid var(--pri);padding:6px 10px;margin:10px 0;background:var(--bg);border-radius:8px}
.pde{font-weight:600}.par{margin-top:4px}
.pex{margin-top:6px;background:var(--okbg);border-radius:6px;padding:6px 10px;font-size:15px}
details.fol{margin-top:10px}details.fol summary{cursor:pointer;color:var(--mute);font-size:14px}