:root{--bg:#f5f7fa;--card:#fff;--ink:#1b2432;--muted:#687383;--line:#dfe4eb;--accent:#2b5f9e;--accent2:#eaf1f9;--good:#27734d;--warn:#9a6b14}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.6 system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif}
.site-head{background:#fff;border-bottom:1px solid var(--line)}.brandrow{max-width:1120px;margin:auto;padding:12px 18px;display:flex;justify-content:space-between;align-items:center}
.brandmark{display:flex;gap:10px;align-items:center;color:var(--ink);text-decoration:none}.brandmark span{display:grid;place-items:center;width:34px;height:34px;border-radius:50%;background:var(--ink);color:white;font-weight:900}.iconbtn{border:0;background:transparent;font-size:1.2rem}
main{max-width:1120px;margin:auto;padding:26px 18px 70px}.view{display:none}.view.active{display:block}.crumb{display:flex;gap:8px;align-items:center;color:var(--muted);font-size:.92rem}.crumb a{color:var(--muted);text-decoration:none}
h1{font-size:clamp(2rem,4.4vw,3.8rem);line-height:1.08;margin:.34em 0 .2em}h2{font-size:clamp(1.45rem,2.5vw,2rem);margin-top:1.7em}.subtitle{font-size:1.14rem;color:var(--muted);max-width:820px}.lead{color:var(--muted);margin-top:-6px}
.route{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}.route-card{background:#fff;border:1px solid var(--line);border-radius:18px;text-align:left;padding:18px;cursor:pointer;min-height:155px;box-shadow:0 7px 18px #1720330a;transition:.15s}.route-card:hover{transform:translateY(-2px);border-color:#aebccd}.route-card .num{display:inline-grid;place-items:center;width:34px;height:34px;border-radius:50%;background:var(--accent2);color:var(--accent);font-weight:900}.route-card h3{font-size:1.18rem;margin:.7em 0 .3em}.route-card p{color:var(--muted);margin:0}
.tools{display:grid;grid-template-columns:1fr 1fr;gap:14px}.tools article,.note,.quickcheck,.labbox,.dashcard,.reviewgrid article{background:#fff;border:1px solid var(--line);border-radius:18px;padding:20px;box-shadow:0 7px 18px #1720330a}.tool-icon{font-size:1.6rem}.fine{font-size:.88rem;color:var(--muted)}
.cta,.ghost,.modulebar button,.labcontrols button,.floatnav button,.modal button{display:inline-block;border:1px solid var(--line);border-radius:11px;padding:9px 13px;background:#fff;color:var(--ink);text-decoration:none;cursor:pointer}.cta{background:var(--accent);color:#fff;border-color:var(--accent);font-weight:700}.ghost:hover,.modulebar button:hover,.labcontrols button:hover{border-color:var(--accent)}
.modulebar{display:flex;justify-content:space-between;align-items:center;color:var(--muted);font-size:.92rem}.actions{display:flex;gap:10px;flex-wrap:wrap;margin:18px 0}.notes{display:grid;grid-template-columns:1fr 1fr;gap:14px}.note h3{margin-top:0}.quickcheck{margin-top:14px;border-left:5px solid var(--accent)}
.methodlist{display:grid;gap:10px}.method{background:#fff;border:1px solid var(--line);border-radius:14px;overflow:hidden}.method summary{padding:14px 16px;font-weight:800;cursor:pointer}.method p{padding:0 16px 16px;margin:0;color:var(--muted)}
.exercisegrid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}.exercisegrid article{background:#fff;border:1px solid var(--line);border-radius:14px;padding:14px}.exercisegrid span{font-weight:800;color:var(--accent)}.exercisegrid p{margin:.4em 0 0}
.quizcard{background:#fff;border:1px solid var(--line);border-radius:18px;padding:20px;margin:14px 0}.option{width:100%;text-align:left;border:1px solid var(--line);background:#fff;border-radius:11px;padding:10px 12px;margin:6px 0;cursor:pointer}.option.correct{background:#eef8f2;border-color:#7eb99a}.option.wrong{background:#fff0f0;border-color:#cf8b8b}.feedback{background:#eef3f9;padding:12px;border-radius:11px;margin-top:12px}.score{font-size:1.5rem;font-weight:900}.axisrow{display:flex;justify-content:space-between;border-bottom:1px solid var(--line);padding:8px 0}
.labcontrols{display:flex;gap:8px;flex-wrap:wrap}.hybvisual{height:260px;position:relative;margin:18px 0;background:linear-gradient(#fff,#f8fafc);border:1px dashed #cfd6df;border-radius:16px}.center{position:absolute;left:50%;top:50%;transform:translate(-50%,-50%);width:44px;height:44px;border-radius:50%;display:grid;place-items:center;background:var(--ink);color:#fff;font-weight:900}.bond{position:absolute;left:50%;top:50%;width:105px;height:4px;background:var(--accent);transform-origin:0 50%;border-radius:4px}.bond:after{content:"";position:absolute;right:-8px;top:-5px;width:14px;height:14px;border-radius:50%;background:var(--accent)}.labtext{font-weight:700}
.reviewgrid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}.reviewgrid article h3{margin-top:0}.progress{height:13px;background:#e6eaf0;border-radius:99px;overflow:hidden}.progress i{height:100%;display:block;background:var(--accent);width:0}.dashrow{display:flex;justify-content:space-between;padding:9px 0;border-bottom:1px solid var(--line)}
.floatnav{position:fixed;right:16px;bottom:16px;display:flex;gap:8px}.floatnav button{box-shadow:0 6px 16px #0002}
.modal{position:fixed;inset:0;background:#0f172a;z-index:50;display:none;color:#fff}.modal.open{display:block}.modalhead{height:58px;display:flex;align-items:center;justify-content:space-between;padding:0 14px;border-bottom:1px solid #ffffff24}.modal button{background:#ffffff14;color:#fff;border-color:#ffffff2c}.slides{height:calc(100% - 58px)}.slide{display:none;height:100%;padding:7vw}.slide.active{display:grid;place-items:center}.slide>div{max-width:900px}.slide h2{font-size:clamp(2rem,5vw,4.5rem);margin:.2em 0}.slide p{font-size:clamp(1.1rem,2.2vw,1.7rem);color:#dbe4f0}
footer{background:#fff;border-top:1px solid var(--line);padding:32px 18px;text-align:center;color:var(--muted)}footer a{color:var(--muted)}
@media(max-width:820px){.route,.exercisegrid,.reviewgrid{grid-template-columns:1fr 1fr}.notes,.tools{grid-template-columns:1fr}}
@media(max-width:540px){.route,.exercisegrid,.reviewgrid{grid-template-columns:1fr}.modulebar{align-items:flex-start;gap:10px}.modulebar span{text-align:right}}