:root{color-scheme:light dark;--bg:#f5f7fc;--ink:#152238;--muted:#526178;--line:#ced7e5;--paper:#fff;--accent:#204fbc;--second:#b04811;--wash:#e7edfa;--good:#216443;--bad:#ac2541;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,'Hiragino Kaku Gothic ProN',Meiryo,sans-serif;color:var(--ink);background:var(--bg);font-size:16px}
@media(prefers-color-scheme:dark){:root{--bg:#101725;--ink:#e8eef9;--muted:#a8b8d0;--line:#34425a;--paper:#172136;--accent:#88adff;--second:#ffb17d;--wash:#202f4a;--good:#8bdbad;--bad:#ffa3b5}}
*{box-sizing:border-box}body{margin:0}a{color:var(--accent);text-underline-offset:.22em}button,input,select{font:inherit}button,select{cursor:pointer}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid var(--second);outline-offset:4px}button{border:1px solid var(--line);background:var(--paper);color:var(--ink);padding:.65rem .9rem;border-radius:5px;min-height:44px}button:hover{border-color:var(--accent)}button[aria-pressed=true]{background:var(--ink);color:var(--bg);border-color:var(--ink)}.skip{position:absolute;left:1rem;top:-10rem;z-index:5}.skip:focus{top:1rem;background:var(--paper);padding:1rem}header{border-bottom:1px solid var(--line)}.topbar{max-width:1360px;margin:auto;padding:1.1rem 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var(--line);gap:2rem;padding-top:1.5rem}.chapters{display:flex;flex-direction:column;gap:.45rem;align-self:start}.chapters button{display:flex;gap:.75rem;text-align:left;align-items:center;background:transparent;border-color:transparent;line-height:1.35}.chapters button span:first-child{font-size:.8rem;color:var(--muted)}.chapters button[aria-pressed=true]{background:var(--wash);color:var(--ink);border-color:var(--line)}.chapter-label{font-size:.8rem;color:var(--muted);margin:.3rem .9rem .65rem}.lesson{min-width:0}.lesson h2{font-family:Georgia,'Yu Mincho',serif;font-size:clamp(1.7rem,2.6vw,2.5rem);font-weight:400;margin:0 0 .7rem}.lead{line-height:1.65;margin:.6rem 0 1.4rem;max-width:760px}.lab{background:var(--paper);border:1px solid var(--line);border-radius:8px;overflow:hidden}.controls{display:flex;gap:1.1rem;flex-wrap:wrap;padding:1.2rem;border-bottom:1px solid var(--line);align-items:end}.control{display:flex;flex-direction:column;gap:.5rem;flex:1 1 180px;max-width:330px;min-width:0;font-size:.9rem}.control input[type=range]{width:100%;accent-color:var(--accent);min-height:30px}.control select{background:var(--paper);color:var(--ink);border:1px solid var(--line);padding:.6rem;min-height:44px;border-radius:4px;width:100%}.buttons{display:flex;gap:.5rem;flex-wrap:wrap}.diagram{width:100%;height:340px;display:block}.diagram text{fill:var(--ink);font-family:inherit;font-size:15px}.diagram .small{font-size:13px;fill:var(--muted)}.diagram .wire{stroke:var(--line);fill:none;stroke-width:1}.diagram .primary{stroke:var(--accent);fill:none;stroke-width:3}.diagram .secondary{stroke:var(--second);fill:none;stroke-width:3;stroke-dasharray:7 4}.diagram .node{fill:var(--paper);stroke:var(--line);stroke-width:1.5}.diagram .point{fill:var(--accent);stroke:var(--paper);stroke-width:2}.diagram .plane{fill:var(--accent);fill-opacity:.15;stroke:var(--accent);stroke-width:1}.result{padding:1rem 1.2rem;border-top:1px solid var(--line);font-variant-numeric:tabular-nums;line-height:1.6;min-height:4rem}.result strong{font-weight:650}.valid{color:var(--good)}.invalid{color:var(--bad)}.legend{display:flex;gap:1.3rem;flex-wrap:wrap;padding:.2rem 1.2rem 1rem;font-size:.85rem;color:var(--muted)}.legend span:before{content:'';display:inline-block;width:22px;border-top:3px solid var(--accent);vertical-align:middle;margin-right:.5rem}.legend span+span:before{border-top:3px dashed var(--second)}.reading{display:grid;grid-template-columns:1.2fr 1fr;gap:2rem;margin-top:1.7rem}.reading p{line-height:1.8;margin:0 0 1.2rem}.formula{font-family:ui-monospace,SFMono-Regular,monospace;line-height:1.9;font-size:.95rem;overflow-wrap:anywhere;border-left:3px solid var(--accent);padding:.7rem 1rem;margin:1rem 0 1.5rem;background:var(--wash)}.reading h3,.closing h3{font-size:.85rem;letter-spacing:.07em;text-transform:uppercase;color:var(--muted);font-weight:600;margin:0 0 .7rem}details{border-top:1px solid 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@media(max-width:800px){main{padding:1.3rem}.topbar{padding:1rem 1.3rem}.workspace{grid-template-columns:1fr;gap:1.1rem}.chapters{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:.3rem}.chapter-label{grid-column:1/-1;margin:0 0 .3rem}.chapters button{padding:.7rem .5rem}.reading{grid-template-columns:1fr;gap:.5rem}.diagram{height:320px}.intro h1{font-size:2.25rem}.toplinks{gap:.8rem}.controls{gap:.8rem}.control{flex-basis:130px}.product-grid{padding:1rem;gap:.5rem}.product-grid div{padding:.8rem .2rem}}
.math-label{text-align:center;display:flex;justify-content:center;align-items:center;min-height:40px;color:var(--ink);font-size:.9rem}.formula{font-family:inherit;overflow-x:auto}.formula .katex-display{margin:.45rem 0;text-align:left}.formula .katex-display>.katex{text-align:left}.result .katex{font-size:1.05em}.reading .katex{font-size:1.05em}.katex-display{max-width:100%}button:disabled{opacity:.45;cursor:default}
@media(prefers-reduced-motion:no-preference){button,a{transition:background-color .15s,color .15s}}