/* BOH4M Course Hub: the course as a transit route. One line per unit, one station per class. */
:root{
  --paper:#F3F6F5; --surface:#FCFDFD; --tint:#E9EFED; --rule:#D5DEDB;
  --ink:#122531; --muted:#4D626C; --soft:#71858D;
  --night:#0F1F29; --night-2:#16303D; --on-night:#EEF4F2; --night-muted:#A7BCC0;
  --u1:#0F766E; --u2:#C98A12; --u3:#2E5BA8; --u4:#8C3A6A;
  --u1-on:#FFFFFF; --u2-on:#1C1404; --u3-on:#FFFFFF; --u4-on:#FFFFFF;
  --u1-text:#0D6B63; --u2-text:#8A5C00; --u3-text:#2A539A; --u4-text:#7E335F;
  --f-display:"Bricolage Grotesque","Segoe UI",system-ui,sans-serif;
  --f-body:"Source Sans 3","Segoe UI",system-ui,sans-serif;
  --side:max(20px, env(safe-area-inset-left, 0px));
  --side-r:max(20px, env(safe-area-inset-right, 0px));
  color-scheme:light;
}
@media (prefers-color-scheme: dark){ :root:not([data-theme="light"]){
  --paper:#0E191F; --surface:#13222A; --tint:#182B33; --rule:#26393F;
  --ink:#E5EDEB; --muted:#A1B4B8; --soft:#83979C;
  --night:#0A141A; --night-2:#132631;
  --u1:#2BB3A3; --u2:#E8B03A; --u3:#7097E0; --u4:#CF79AA;
  --u1-on:#06201C; --u2-on:#1C1404; --u3-on:#081428; --u4-on:#240A19;
  --u1-text:#4FC7B8; --u2-text:#F0C060; --u3-text:#93B2EC; --u4-text:#DD95BD;
  color-scheme:dark;
}}
:root[data-theme="dark"]{
  --paper:#0E191F; --surface:#13222A; --tint:#182B33; --rule:#26393F;
  --ink:#E5EDEB; --muted:#A1B4B8; --soft:#83979C;
  --night:#0A141A; --night-2:#132631;
  --u1:#2BB3A3; --u2:#E8B03A; --u3:#7097E0; --u4:#CF79AA;
  --u1-on:#06201C; --u2-on:#1C1404; --u3-on:#081428; --u4-on:#240A19;
  --u1-text:#4FC7B8; --u2-text:#F0C060; --u3-text:#93B2EC; --u4-text:#DD95BD;
  color-scheme:dark;
}
.u1{--line:var(--u1);--on:var(--u1-on);--ltext:var(--u1-text)}
.u2{--line:var(--u2);--on:var(--u2-on);--ltext:var(--u2-text)}
.u3{--line:var(--u3);--on:var(--u3-on);--ltext:var(--u3-text)}
.u4{--line:var(--u4);--on:var(--u4-on);--ltext:var(--u4-text)}

*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:132px;-webkit-text-size-adjust:100%}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
body.hub{margin:0;background:var(--paper);color:var(--ink);font-family:var(--f-body);font-size:18px;line-height:1.55;font-kerning:normal}
[hidden]{display:none!important}
a{color:inherit}
h1,h2,h3{font-family:var(--f-display);margin:0;text-wrap:balance}
p{margin:0}
.wrap{max-width:1160px;margin:0 auto;padding-left:var(--side);padding-right:var(--side-r)}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.skip{position:absolute;left:12px;top:-60px;background:var(--surface);color:var(--ink);padding:10px 14px;border-radius:8px;z-index:20;font-weight:700}
.skip:focus{top:12px}
:focus-visible{outline:3px solid var(--u2);outline-offset:3px;border-radius:4px}

/* Nav */
.nav{background:var(--night);color:var(--on-night);padding-top:env(safe-area-inset-top,0px)}
.nav-in{display:flex;align-items:center;justify-content:space-between;gap:16px;min-height:64px}
.brand{display:flex;align-items:center;gap:12px;text-decoration:none;font-family:var(--f-display);font-weight:650;font-size:1.06rem;letter-spacing:-.005em}
.brand-mark{width:40px;height:16px;flex:none}
.brand-mark path{stroke:var(--night-muted);stroke-width:2}
.brand-mark circle:nth-of-type(1){fill:#2BB3A3}.brand-mark circle:nth-of-type(2){fill:#E8B03A}.brand-mark circle:nth-of-type(3){fill:#7097E0}
.nav-links{display:flex;gap:4px}
.nav-links a{text-decoration:none;color:var(--night-muted);font-weight:600;font-size:.98rem;padding:8px 12px;border-radius:8px}
.nav-links a:hover{color:var(--on-night);background:var(--night-2)}

/* Hero */
.hero{background:var(--night);color:var(--on-night);padding-block:56px 64px;overflow:hidden}
.kicker{color:var(--night-muted);font-weight:600;font-size:1rem}
.hero h1{font-size:clamp(2.7rem,7.2vw,5.6rem);font-weight:700;line-height:1;letter-spacing:-.022em;margin-top:14px;font-variation-settings:"opsz" 96}
.lead{max-width:62ch;margin-top:22px;font-size:1.18rem;line-height:1.6;color:#C9D7D9}

.route{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));margin-top:52px}
.seg{min-width:0;display:flex;flex-direction:column;gap:14px}
.seg-name{text-decoration:none;font-size:.98rem;color:var(--night-muted);padding-right:16px;min-height:2.9em}
.seg-name b{display:block;color:var(--line);font-family:var(--f-display);font-weight:700;font-size:1.05rem}
.seg-name:hover{color:var(--on-night)}
.track{position:relative;display:flex;align-items:center;justify-content:space-between;height:34px;padding-inline:2px}
.track::before{content:"";position:absolute;left:0;right:0;top:50%;height:6px;margin-top:-3px;background:var(--line)}
.seg:first-child .track::before{left:9px;border-radius:3px 0 0 3px}
.seg:last-child .track::before{right:13px;border-radius:0 3px 3px 0}
.st,.ix{position:relative;display:grid;place-items:center;width:22px;height:34px;flex:none;text-decoration:none}
.st span{width:16px;height:16px;border-radius:50%;background:var(--night);border:3px solid var(--line);transition:transform .15s}
.st.ready span{background:var(--line);width:18px;height:18px}
.ix{width:28px}
.ix span{width:26px;height:26px;border-radius:50%;background:var(--on-night);border:5px solid var(--night);box-shadow:0 0 0 3px var(--line)}
.ix:not(.ready) span{background:var(--night-2)}
.st:hover span,.st:focus-visible span{transform:scale(1.3)}
.st::after,.ix::after{content:attr(data-tip);position:absolute;bottom:calc(100% + 4px);left:50%;transform:translateX(-50%);background:var(--on-night);color:var(--night);font-size:.85rem;font-weight:700;padding:5px 9px;border-radius:6px;white-space:nowrap;pointer-events:none;opacity:0;transition:opacity .12s;z-index:3}
.st:hover::after,.st:focus-visible::after,.ix:hover::after,.ix:focus-visible::after{opacity:1}
.seg:first-child .st:first-child::after{left:0;transform:none}
.seg:last-child .ix:last-child::after{left:auto;right:0;transform:none}
.seg-ends{display:flex;justify-content:space-between;font-size:.9rem;color:var(--night-muted);font-variant-numeric:tabular-nums;padding-inline:4px 16px}
.seg-ends span:nth-child(2){color:var(--on-night);font-weight:600}
.route-key{display:flex;flex-wrap:wrap;align-items:center;gap:10px 24px;margin-top:30px;font-size:.95rem;color:var(--night-muted)}
.route-key span{display:inline-flex;align-items:center;gap:8px}
.k-dot{width:14px;height:14px;border-radius:50%;border:3px solid #7FA2A6;background:var(--night)}
.k-dot.k-ready{background:#7FA2A6}
.k-int{width:16px;height:16px;border-radius:50%;background:var(--on-night);box-shadow:0 0 0 3px #7FA2A6}
.route-count{margin-left:auto;color:var(--on-night)!important;font-weight:700;font-size:1.02rem}
@media (prefers-reduced-motion:no-preference){
  .st span,.ix span{animation:pop .5s cubic-bezier(.3,1.5,.6,1) both;animation-delay:calc(var(--i,0) * 18ms + 150ms)}
  @keyframes pop{from{transform:scale(0)}to{transform:scale(1)}}
}

/* How a class runs */
.how{padding-block:72px 64px;border-bottom:1px solid var(--rule)}
.how h2,.teachers h2{font-size:clamp(1.9rem,3.6vw,2.6rem);font-weight:700;letter-spacing:-.02em}
.sub{margin-top:10px;color:var(--muted);max-width:62ch;font-size:1.1rem}
.timeline{list-style:none;padding:0;margin:34px 0 0;display:flex;gap:4px;min-height:92px}
.timeline li{flex:var(--m) 1 0;min-width:0;background:var(--tint);border-radius:6px;padding:14px 14px 12px;display:flex;flex-direction:column;justify-content:space-between;gap:10px}
.timeline li:first-child{border-radius:12px 6px 6px 12px}
.timeline li:last-child{border-radius:6px 12px 12px 6px}
.timeline b{font-family:var(--f-display);font-weight:650;font-size:1.02rem;line-height:1.15}
.timeline span{color:var(--muted);font-size:.9rem;font-variant-numeric:tabular-nums}
.timeline .t-game{background:var(--ink);color:var(--paper)}
.timeline .t-game span{color:var(--soft)}
.three{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:36px;margin-top:44px}
.three h3{font-size:1.2rem;font-weight:650;padding-top:16px;border-top:2px solid var(--ink)}
.three p{color:var(--muted);margin-top:8px;max-width:38ch}

/* Finder */
.finder{position:sticky;top:0;z-index:8;background:color-mix(in srgb,var(--paper) 92%,transparent);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);border-bottom:1px solid var(--rule);padding-top:env(safe-area-inset-top,0px)}
.finder-in{display:flex;align-items:center;gap:12px;min-height:64px}
.unit-jump{display:flex;gap:4px;flex:1;min-width:0;overflow-x:auto;scrollbar-width:none}
.unit-jump::-webkit-scrollbar{display:none}
.unit-jump a{display:inline-flex;align-items:center;gap:8px;white-space:nowrap;text-decoration:none;font-weight:650;font-size:.96rem;padding:8px 12px;border-radius:8px;color:var(--ink)}
.unit-jump a:hover{background:var(--tint)}
.unit-jump i{width:10px;height:10px;border-radius:50%;background:var(--line)}
.unit-jump span{color:var(--muted);font-weight:500}
.search{display:flex;align-items:center;gap:8px;background:var(--surface);border:1px solid var(--rule);border-radius:10px;padding:0 12px;height:42px;flex:0 1 250px;min-width:0}
@media (max-width:1380px){.unit-jump span{display:none}}
.search svg{width:18px;height:18px;fill:none;stroke:var(--soft);stroke-width:2;flex:none}
.search input{border:0;background:transparent;font:inherit;font-size:.98rem;color:var(--ink);width:100%;min-width:0;outline:none}
.search:focus-within{outline:3px solid var(--u2);outline-offset:2px}

/* Units */
.unit{padding-block:64px 24px}
.unit-head{display:grid;grid-template-columns:150px minmax(0,1fr) 200px;gap:28px;align-items:start}
.unit-tag{background:var(--line);color:var(--on);border-radius:14px;padding:16px 18px;display:flex;flex-direction:column;gap:2px}
.unit-tag span:first-child{font-family:var(--f-display);font-weight:700;font-size:1.5rem;line-height:1.1}
.unit-tag span:last-child{font-size:.92rem;font-weight:600;opacity:.9}
.unit-text h2{font-size:clamp(1.9rem,3.8vw,2.8rem);font-weight:700;letter-spacing:-.025em;line-height:1.05}
.unit-purpose{margin-top:10px;color:var(--muted);font-size:1.1rem;max-width:60ch}
.unit-project{margin-top:12px;font-size:.98rem;max-width:66ch;color:var(--muted)}
.unit-project b{color:var(--ltext)}
.unit-meter{display:flex;flex-direction:column;gap:4px;padding-top:6px}
.unit-meter b{font-family:var(--f-display);font-size:2.4rem;line-height:1;font-weight:700;font-variant-numeric:tabular-nums}
.unit-meter span{color:var(--muted);font-size:.95rem}
.unit-meter i{display:block;height:6px;border-radius:3px;background:linear-gradient(90deg,var(--line) var(--p),var(--rule) var(--p));margin-top:6px}

.line{list-style:none;margin:36px 0 0;padding:0 0 0 56px;position:relative}
.line::before{content:"";position:absolute;left:21px;top:30px;bottom:30px;width:6px;border-radius:3px;background:var(--line)}
.cl{position:relative;display:grid;grid-template-columns:minmax(0,1fr) auto;gap:10px 28px;align-items:center;padding:22px 4px 22px 8px;border-bottom:1px solid var(--rule)}
.cl:last-child{border-bottom:0}
.node{position:absolute;left:-44px;top:50%;margin-top:-11px;width:22px;height:22px;border-radius:50%;background:var(--paper);border:4px solid var(--line)}
.cl.ready .node{background:var(--line);box-shadow:0 0 0 3px var(--paper)}
.cl-num{font-size:.92rem;font-weight:700;color:var(--ltext);font-variant-numeric:tabular-nums}
.cl h3{font-size:1.32rem;font-weight:650;letter-spacing:-.01em;line-height:1.2;margin-top:2px}
.cl-q{margin-top:6px;max-width:68ch}
.cl-k{margin-top:4px;color:var(--muted);font-size:.96rem;max-width:68ch}
.cl:not(.ready) h3,.cl:not(.ready) .cl-q{color:var(--muted)}
.cl-acts{display:flex;gap:8px;flex-wrap:wrap;justify-content:flex-end}
.btn{display:inline-flex;align-items:center;gap:8px;height:42px;padding:0 16px;border-radius:10px;border:1.5px solid var(--rule);background:var(--surface);color:var(--ink);text-decoration:none;font-weight:650;font-size:.98rem;white-space:nowrap}
.btn svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:1.8;stroke-linejoin:round;stroke-linecap:round}
.btn:hover{border-color:var(--ink)}
.btn.solid{background:var(--line);border-color:var(--line);color:var(--on)}
.btn.solid svg[viewBox] path[d^="M6 4"]{fill:currentColor}
.btn.solid:hover{filter:brightness(1.08)}
.soon{color:var(--soft);font-weight:600;font-size:.95rem}
.cl.check{background:var(--tint);border-bottom-color:transparent;border-radius:12px;margin-block:8px;padding-inline:20px 16px}
.cl.check .node{left:-48px;width:30px;height:30px;margin-top:-15px;background:var(--surface);border:6px solid var(--paper);box-shadow:0 0 0 4px var(--line)}
.cl.check.ready .node{background:var(--ink)}
.cl.check .cl-num{color:var(--muted)}
.cl.hit{animation:hit 1.6s ease-out}
@keyframes hit{0%{background:color-mix(in srgb,var(--line) 26%,transparent)}100%{background:transparent}}
.cl.check.hit{animation:none}
@media (prefers-reduced-motion:reduce){.cl.hit{animation:none}}
.empty{margin:40px 0;padding:28px;border:1px dashed var(--rule);border-radius:12px;color:var(--muted);text-align:center}

/* Teachers + footer */
.teachers{padding-block:72px;margin-top:48px;background:var(--surface);border-top:1px solid var(--rule)}
.teachers-in{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.4fr);gap:48px}
.teachers p{margin-top:12px;color:var(--muted);max-width:52ch}
.tips{margin:0;display:grid;grid-template-columns:1fr 1fr;gap:28px 32px}
.tips dt{font-family:var(--f-display);font-weight:650;font-size:1.08rem}
.tips dd{margin:6px 0 0;color:var(--muted)}
.foot{background:var(--night);color:var(--night-muted);padding-block:28px calc(28px + env(safe-area-inset-bottom,0px));font-size:.95rem}
.foot-in{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}

/* Small screens */
@media (max-width:980px){
  .route{grid-template-columns:repeat(2,minmax(0,1fr));row-gap:28px}
  .seg:nth-child(2) .track::before{right:13px;border-radius:0 3px 3px 0}
  .seg:nth-child(3) .track::before{left:9px;border-radius:3px 0 0 3px}
  .unit-head{grid-template-columns:minmax(0,1fr) 170px}
  .unit-tag{grid-column:1 / -1;flex-direction:row;gap:12px;align-items:baseline;justify-self:start}
  .unit-tag span:first-child{font-size:1.2rem}
  .teachers-in{grid-template-columns:1fr;gap:28px}
}
@media (max-width:720px){
  html{scroll-padding-top:120px}
  .nav-links{display:none}
  .hero{padding-block:40px 48px}
  .route{grid-template-columns:1fr}
  .seg .track::before{left:9px!important;right:13px!important;border-radius:3px!important}
  .seg-name{min-height:0}
  .three{grid-template-columns:1fr;gap:24px}
  .timeline{flex-wrap:wrap}
  .timeline li{flex:1 1 30%;border-radius:8px!important}
  .finder-in{flex-wrap:wrap;padding-block:10px;gap:8px}
  .unit-jump span{display:none}
  .search{flex:1 1 100%}
  .unit-head{grid-template-columns:1fr;gap:16px}
  .line{padding-left:40px}
  .line::before{left:13px}
  .node{left:-36px}
  .cl.check .node{left:-40px}
  .cl{grid-template-columns:1fr}
  .cl-acts{justify-content:flex-start}
  .tips{grid-template-columns:1fr}
}