:root{
  --bg:#f4f8f7;--card:#fff;--text:#17312f;--muted:#647773;--line:#d8e3e1;
  --accent:#0f766e;--soft:#ecfdf5;--warm:#fff7ed;
}
*{box-sizing:border-box}
html{font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;background:var(--bg);color:var(--text)}
body{margin:0}
button,input,select{font:inherit}
button{min-height:44px;border:1px solid var(--line);border-radius:12px;background:#fff;color:var(--text);padding:9px 13px;font-weight:750;cursor:pointer}
button:hover{border-color:#90aaa5}
button.active,button.primary{background:var(--accent);color:#fff;border-color:var(--accent)}
button:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #99f6e4;outline-offset:2px}
.topbar{padding:20px max(16px,calc((100% - 1180px)/2));background:#fff;border-bottom:1px solid var(--line)}
.topbar h1{margin:0;font-size:clamp(1.45rem,4vw,2.2rem)}
.topbar h1 span{font-size:.78rem;background:var(--soft);color:var(--accent);padding:4px 8px;border-radius:999px;vertical-align:middle}
.topbar p{margin:6px 0 0;color:var(--muted)}
main{width:min(1180px,calc(100% - 24px));margin:16px auto 40px}
.tabs{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:14px}
.tabs button{flex:1;min-width:150px}
.tab{display:none}.tab.active{display:block}
.card{background:var(--card);border:1px solid var(--line);border-radius:18px;padding:16px;box-shadow:0 8px 24px rgba(23,49,47,.045);margin-bottom:14px}
.section-head{display:flex;gap:12px;justify-content:space-between;align-items:end;flex-wrap:wrap;margin-bottom:12px}
.section-head h2{margin:0;font-size:1.12rem}.section-head p{margin:4px 0 0;color:var(--muted);font-size:.88rem}
.shape-buttons{display:grid;grid-template-columns:repeat(9,minmax(0,1fr));gap:8px}
.shape-buttons button{min-height:72px;display:grid;place-items:center;gap:2px;padding:8px 4px}
.shape-buttons .icon{font-size:1.45rem}.shape-buttons small{font-size:.72rem}
.two-col{display:grid;grid-template-columns:1.08fr .92fr;gap:14px}
#solidCanvas{display:block;width:100%;height:auto;border:1px solid var(--line);border-radius:14px;background:linear-gradient(180deg,#fbfdfd,#eef7f5);touch-action:none}
.btn-row{display:flex;gap:8px;flex-wrap:wrap}
.range-row{display:grid;grid-template-columns:auto minmax(100px,1fr) auto;gap:10px;align-items:center;margin-top:12px}
.range-row label{color:var(--muted);font-size:.86rem}
.net-view{min-height:330px;display:flex;align-items:center;justify-content:center;border:1px solid var(--line);border-radius:14px;background:#fbfdfd;padding:10px;overflow:hidden}
.net-view svg{max-width:100%;height:auto;max-height:320px}
.net-note,.explain{margin-top:10px;padding:10px 12px;background:#f8fbfa;border-radius:12px;color:var(--muted);font-size:.88rem;line-height:1.55}
.check{display:flex;gap:6px;align-items:center;font-size:.86rem;color:var(--muted)}
.facts-grid{display:grid;grid-template-columns:repeat(3,1fr) 2.2fr;gap:10px}
.facts-grid>div,.result-grid>div{padding:14px;border-radius:14px;background:#f8fbfa;border:1px solid var(--line)}
.facts-grid span,.result-grid span{display:block;color:var(--muted);font-size:.8rem;margin-bottom:5px}
.facts-grid b,.result-grid b{font-size:1.05rem}
.input-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}
.input-grid label{display:grid;gap:6px;font-weight:700;font-size:.88rem}
.input-grid input,.input-grid select{width:100%;min-height:44px;border:1px solid var(--line);border-radius:10px;padding:8px 10px;background:#fff}
.result-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}
.practice-card{max-width:780px;margin-inline:auto}
.practice-status{display:flex;justify-content:space-between;gap:10px;padding:10px 12px;background:#f8fbfa;border-radius:12px}
.question{font-size:1.15rem;font-weight:850;line-height:1.5;padding:24px 4px 16px;text-align:center}
.answers{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}
.answers button{min-height:58px}
.answers button.correct{background:#ecfdf5;border-color:#34d399;color:#065f46}
.answers button.wrong{background:#fff1f2;border-color:#fb7185;color:#9f1239}
.feedback{min-height:48px;padding:12px 0;font-weight:750}
footer{width:min(1180px,calc(100% - 24px));margin:0 auto 32px;padding-top:12px;border-top:1px solid var(--line);display:flex;justify-content:space-between;gap:10px;flex-wrap:wrap;color:var(--muted);font-size:.82rem}
@media(max-width:920px){.shape-buttons{grid-template-columns:repeat(5,minmax(0,1fr))}.two-col{grid-template-columns:1fr}.facts-grid{grid-template-columns:repeat(3,1fr)}.facts-grid .wide{grid-column:1/-1}}
@media(max-width:560px){main{width:min(100% - 16px,1180px)}.shape-buttons{grid-template-columns:repeat(3,minmax(0,1fr))}.card{padding:13px;border-radius:15px}.input-grid,.result-grid{grid-template-columns:1fr}.answers{grid-template-columns:1fr}.facts-grid{grid-template-columns:repeat(3,1fr)}.net-view{min-height:280px}}