:root{--bg:#fbfaf6;--ink:#1d2230;--mute:#5b6273;--line:#dedad0;--card:#fff;--acc:#1f6feb;--acc2:#e8590c;--ok:#2b8a3e;--bad:#c92a2a}
@media (prefers-color-scheme:dark){:root:not(.printpage){--bg:#11141b;--ink:#e9ecf2;--mute:#a3abbd;--line:#2b3140;--card:#181c25;--acc:#6ea8ff;--acc2:#ff9b5e}}
*{box-sizing:border-box}html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:17px/1.6 system-ui,-apple-system,"Segoe UI",Roboto,Arial,sans-serif}
a{color:var(--acc)}h1{font-size:2rem;line-height:1.2;margin:.4em 0 .3em}h2{font-size:1.4rem;margin:1.6em 0 .5em}h3{font-size:1.1rem;margin:1em 0 .3em}
.snav{display:flex;flex-wrap:wrap;gap:12px;justify-content:space-between;align-items:center;padding:12px 16px;border-bottom:1px solid var(--line)}
.snav .logo{font-weight:800;text-decoration:none;color:var(--ink)}.snav .logo span{color:var(--acc2)}.snav nav{display:flex;gap:16px;flex-wrap:wrap}.snav nav a{text-decoration:none}
.smain{max-width:860px;margin:0 auto;padding:16px}
.crumb{font-size:.9rem;color:var(--mute)}.lead{font-size:1.15rem;color:var(--mute)}.small{font-size:.88rem;color:var(--mute)}.meta{color:var(--mute);font-size:.92rem}
.tools{display:flex;flex-wrap:wrap;gap:8px;margin:12px 0}.btn{display:inline-block;padding:9px 14px;border-radius:10px;background:var(--acc);color:#fff;text-decoration:none;border:0;font:inherit;font-weight:600;cursor:pointer}
.btn.ghost{background:transparent;color:var(--acc);border:1px solid var(--acc)}
.toc{display:flex;gap:8px;flex-wrap:wrap;position:sticky;top:0;background:var(--bg);padding:8px 0;z-index:2;border-bottom:1px solid var(--line)}.toc a{padding:4px 12px;border-radius:20px;border:1px solid var(--line);text-decoration:none}
section{scroll-margin-top:60px}.cite{font-size:.72em;vertical-align:super;text-decoration:none;margin-left:2px}
.exp{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:4px 18px 14px;margin-top:24px}
.cols{display:grid;grid-template-columns:1fr 1fr;gap:16px}@media (max-width:640px){.cols{grid-template-columns:1fr}}
details{margin:12px 0;padding:10px 14px;border-radius:10px;background:var(--bg);border:1px dashed var(--line)}summary{cursor:pointer;font-weight:700}
.game{position:relative;border-radius:14px;overflow:hidden;border:1px solid var(--line);background:#0e1320}.game canvas{display:block;width:100%;height:auto;touch-action:manipulation}
.gui{display:flex;flex-wrap:wrap;gap:8px;justify-content:center;padding:10px;background:var(--card)}.gui button{font:inherit;font-weight:700;padding:10px 16px;border-radius:10px;border:2px solid var(--acc);background:var(--card);color:var(--ink);cursor:pointer;min-width:110px}
.gui button:hover{background:var(--acc);color:#fff}.gui .msg{width:100%;text-align:center;font-weight:600}
.quiz .qq{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:12px 16px;margin:10px 0}.quiz .qq p{margin:.2em 0 .6em;font-weight:600}
.quiz button{display:block;width:100%;text-align:left;font:inherit;padding:9px 12px;margin:6px 0;border-radius:9px;border:1px solid var(--line);background:var(--bg);color:var(--ink);cursor:pointer}
.quiz button.ok{border-color:var(--ok);background:color-mix(in srgb,var(--ok) 15%,var(--bg))}.quiz button.no{border-color:var(--bad);background:color-mix(in srgb,var(--bad) 12%,var(--bg))}
.quiz .fb{font-size:.95rem;color:var(--mute)}.quiz .score{font-weight:800;font-size:1.1rem}
.ages{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:14px;margin:18px 0}.agecard{display:flex;flex-direction:column;gap:4px;padding:16px;border-radius:14px;border:1px solid var(--line);background:var(--card);text-decoration:none;color:var(--ink)}
.agecard b{color:var(--acc2);font-size:1.1rem}.agecard span{font-weight:700}.agecard small{color:var(--mute)}
.src{border:1px solid var(--line);background:var(--card);border-radius:12px;padding:6px 16px;margin:12px 0}.src h3{margin-top:.6em}.link{word-break:break-all}
.rate{font-weight:700;padding:1px 8px;border-radius:8px}.rhigh{background:#d3f9d8;color:#1b5e20}.rmedium{background:#fff3bf;color:#7a5b00}
.howwe{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:4px 16px}
.other{margin-top:28px}.sfoot{max-width:860px;margin:30px auto 0;padding:16px;border-top:1px solid var(--line);font-size:.85rem;color:var(--mute)}
/* worksheet + teacher sheet */
.printpage{background:#fff;color:#111}.printpage .smain{max-width:800px}.sheet h1{font-size:1.6rem;margin:.1em 0}.sheet h2{font-size:1.15rem;margin:1em 0 .3em;border-bottom:2px solid #111}
.sheet p{margin:.3em 0}.kicker{font-size:.8rem;text-transform:uppercase;letter-spacing:.06em;color:#555}
.shead{display:flex;gap:16px;justify-content:space-between;align-items:flex-start}.qrbox{text-align:center;font-size:.75rem;line-height:1.3;flex:none}.qrbox .qr{width:120px;height:120px}.qrbox .url{font-weight:700;word-break:break-all;max-width:150px}
.namerow{margin-top:10px!important}.namerow span{display:inline-block;width:170px;border-bottom:1px solid #111;margin:0 14px 0 4px}
.rt{border-collapse:collapse;width:100%;margin:8px 0;font-size:.92rem}.rt th,.rt td{border:1px solid #333;padding:6px 8px;text-align:left;vertical-align:top}.rt td{height:30px}.rt th{background:#f1f1f1}.rt small{color:#777}
.work li{margin-bottom:10px}.lines i{display:block;border-bottom:1px solid #999;height:26px}.drawbox{border:1px solid #999;height:110px;width:160px;display:flex;align-items:center;justify-content:center;font-size:40px;border-radius:8px}
.opts{font-weight:700;letter-spacing:.05em}.tight li{margin:2px 0}.srcnote{font-size:.8rem;color:#555;margin-top:12px!important}
@page{size:A4;margin:12mm}
@media print{.snav,.toc,.tools,.noprint,.game,.sfoot,#play,#quiz,.other{display:none!important}body{background:#fff;color:#000;font-size:11.5pt}.smain{padding:0;max-width:none}a{color:#000;text-decoration:none}
 details{border:0;padding:0}details>*{display:block}.sheet h2{break-after:avoid}.rt,.work li,.src{break-inside:avoid}}
.langbar{font-size:.88rem;color:var(--mute);margin:0 0 6px}.langbar b{color:var(--ink)}.langbar a{margin:0 3px}.tnote{font-style:italic}