:root{color-scheme:dark;--bg:#07131e;--panel:#0e2232;--line:#294858;--muted:#adc0cb;--blue:#78cbff;--mint:#70e6d2}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:#eef6fa;font:16px/1.65 system-ui,'Nirmala UI',sans-serif;background-image:linear-gradient(#19344744 1px,transparent 1px),linear-gradient(90deg,#19344744 1px,transparent 1px);background-size:44px 44px}a{color:var(--blue);text-underline-offset:5px}button,.button{display:inline-block;background:var(--mint);color:#07131e;border:1px solid var(--mint);border-radius:5px;padding:12px 20px;font:600 1rem system-ui;cursor:pointer;text-decoration:none}button:hover,.button:hover{filter:brightness(1.12)}button:disabled{opacity:.65;cursor:default}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #ffcc78;outline-offset:4px}header{display:flex;justify-content:space-between;align-items:center;gap:20px;padding:24px max(5vw,20px);background:#07131ef0;border-bottom:1px solid var(--line)}.brand{display:flex;gap:14px;color:#eef6fa;text-decoration:none;font-size:24px}.brand b,.splash-c{border:1px solid var(--blue);padding:0 14px;color:var(--blue);font-size:36px}.brand small{display:block;font-size:14px;color:var(--muted)}.actions{display:flex;align-items:center;gap:14px}.actions button{background:transparent;color:var(--blue);font-size:14px;padding:8px 12px}nav{display:flex;gap:24px;padding:14px 5vw;flex-wrap:wrap;background:#0a1a27}nav a{font-size:14px;text-decoration:none}nav a.active{color:var(--mint);text-decoration:underline}main{max-width:1240px;margin:auto;padding:50px 24px 70px;min-height:70vh}h1{font-size:clamp(2.1rem,4.5vw,4.5rem);line-height:1.1;letter-spacing:-.035em;margin:20px 0 28px}h2{line-height:1.3;font-size:1.5rem}h3{line-height:1.3}p{max-width:78ch}.eyebrow{font-size:14px;letter-spacing:.15em;color:var(--mint)}.muted,small{color:var(--muted)}.hero{display:grid;grid-template-columns:1.2fr 1fr;gap:50px;align-items:center;padding:30px 0 60px}.hero h1 em{font-style:normal;color:var(--blue)}.hero .art{border:1px solid var(--line);background:#0e223299;padding:25px}.hero .art p{font-size:14px}.grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}.card{padding:26px;background:var(--panel);border:1px solid var(--line);border-radius:7px;min-width:0}.card p{color:var(--muted)}.stats{display:flex;gap:40px;border-block:1px solid var(--line);padding:22px 0;margin-bottom:38px;flex-wrap:wrap}.stats strong{display:block;font-size:22px;color:var(--blue)}.tools{display:flex;flex-wrap:wrap;gap:10px;margin:28px 0}.tools button{background:transparent;color:var(--muted);border-color:var(--line);font-size:14px;padding:10px 14px}.tools button.selected{background:var(--mint);color:var(--bg)}.calculator{display:grid;grid-template-columns:1fr 1.2fr;gap:22px}.field{display:block;margin:18px 0}.field span{display:block;margin-bottom:6px;font-size:14px;color:var(--muted)}input,select{width:100%;padding:13px;background:var(--bg);color:#fff;border:1px solid var(--line);border-radius:4px;font:1rem system-ui}input[type=checkbox]{width:auto;margin-right:12px}.check{display:block;margin:15px 0}.formula{white-space:pre-wrap;background:var(--bg);border-left:3px solid var(--blue);padding:18px;font:14px/1.8 ui-monospace,monospace;overflow-wrap:anywhere}.result{font-size:2.4rem;color:var(--mint);line-height:1.5}.result small{font-size:1rem}.notice,.source-note{font-size:14px;border-top:1px solid var(--line);padding-top:16px;color:var(--muted)}.error,.warning{color:#ffd08b}.engineering-svg{width:100%;color:var(--blue);max-height:280px}.engineering-svg text{fill:var(--muted);font-size:14px}.part-fill,.core{fill:#183d51;stroke:var(--blue);stroke-width:2}.core{fill:#07131e}.fine,.dimension{fill:none;stroke:var(--blue);stroke-width:1.5}.belt-running{fill:none;stroke:var(--mint);stroke-width:5}.guide summary{cursor:pointer;font-size:20px;font-weight:600}.guide{margin:18px 0}.guide p{color:var(--muted)}footer{display:flex;gap:25px;flex-wrap:wrap;padding:24px 5vw;border-top:1px solid var(--line);color:var(--muted);font-size:14px}#splash{position:fixed;inset:0;z-index:10;background:var(--bg);display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center;padding:24px}#splash[hidden]{display:none}.splash-c{margin-top:30px;font-size:70px;padding:0 35px}.skip{position:absolute;left:-9999px}.skip:focus{left:20px;top:10px;z-index:20;background:var(--bg);padding:10px}@media(max-width:800px){.hero,.calculator{grid-template-columns:1fr}.hero{gap:20px}.grid{grid-template-columns:1fr 1fr}header{flex-wrap:wrap}.actions{flex-wrap:wrap}main{padding:28px 18px 50px}nav{gap:16px}.stats{gap:24px}}@media(max-width:500px){.grid{grid-template-columns:1fr}.card{padding:20px}.hero .art{padding:12px}footer{display:grid}.actions{gap:10px}.brand{font-size:22px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto}}