body{background:#f5f7fa;margin:0;font-family:system-ui,-apple-system,BlinkMacSystemFont}header{color:#fff;text-align:center;background:#1e40af;padding:16px}nav{background:#fff;border-bottom:1px solid #ddd;display:flex;overflow-x:auto}nav button{cursor:pointer;background:0 0;border:none;flex:1;padding:12px}nav button.active{border-bottom:3px solid #1e40af;font-weight:600}section{padding:16px;display:none}section.active{display:block}.card{background:#fff;border-radius:8px;margin-bottom:16px;padding:16px;box-shadow:0 2px 6px #0000000d}input[type=number]{border:1px solid #ccc;border-radius:6px;width:100%;margin:8px 0;padding:10px;font-size:16px}.note{color:#555;margin-top:6px;font-size:13px}.formula{color:#1e40af;margin-top:4px;font-size:13px}.aka-desc{color:#228b22;margin-top:4px;font-size:13px}