/* Layout: three-pane study desk — courses rail | dialogue | the coach's notebook. Stacks on phones. */
:root{
  --paper:#F7F8F6; --surface:#FFFFFF; --ink:#1B2230; --muted:#5B6474; --line:#DCE0E4;
  --accent:#1F5F7A; --accent-ink:#FFFFFF; --accent-soft:#E3EEF3;
  --mark:#F0D24A; --mark-soft:#FBF3C9; --danger:#A33A2E; --ok:#2E7555; --student:#EEF1F4;
  --f-display:"Source Serif 4", Georgia, "Times New Roman", serif;
  --f-ui:"IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --f-mono:"IBM Plex Mono", ui-monospace, Menlo, Consolas, monospace;
  --r:10px; color-scheme:light;
}
@media (prefers-color-scheme: dark){:root{
  --paper:#11151B; --surface:#181D25; --ink:#E4E8EE; --muted:#9AA3B1; --line:#2A313C;
  --accent:#72B6D2; --accent-ink:#0D1B22; --accent-soft:#1B2C36;
  --mark:#E6C743; --mark-soft:#3A3417; --danger:#E0786B; --ok:#6CC49A; --student:#222935; color-scheme:dark;
}}
*{box-sizing:border-box}
html,body{height:100%;margin:0}
body{background:var(--paper);color:var(--ink);font-family:var(--f-ui);font-size:15px;line-height:1.5}
button,input,textarea,select{font:inherit;color:inherit}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
[hidden]{display:none!important}
h1,h2,h3{font-family:var(--f-display);font-weight:600;margin:0;text-wrap:balance}
.muted,.sub{color:var(--muted);margin:0}
.sub{font-size:.85rem}
.app{display:flex;flex-direction:column;height:100%}
header.top{display:flex;align-items:center;gap:16px;flex-wrap:wrap;padding:10px 16px;border-bottom:1px solid var(--line);background:var(--surface)}
.brand{font-family:var(--f-display);font-weight:600;font-size:1.2rem}
.brand small{display:block;font-family:var(--f-mono);font-size:.68rem;font-weight:400;letter-spacing:.08em;text-transform:uppercase;color:var(--muted)}
.tabs{display:flex;gap:4px;margin-left:auto;flex-wrap:wrap}
.tab{border:1px solid transparent;background:none;padding:6px 12px;border-radius:999px;cursor:pointer;color:var(--muted);font-weight:500}
.tab[aria-selected="true"]{background:var(--accent-soft);color:var(--ink);border-color:var(--line)}
.banner{padding:10px 16px;background:var(--mark-soft);border-bottom:1px solid var(--line);font-size:.9rem}
main{flex:1;min-height:0;display:flex}
.view{flex:1;min-height:0;display:none}
.view.on{display:flex}

.auth{margin:auto;width:100%;max-width:420px;padding:24px 16px;display:flex;flex-direction:column;gap:12px}
.panel{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);padding:18px;display:flex;flex-direction:column;gap:14px;min-width:0}
.label{font-family:var(--f-mono);font-size:.68rem;letter-spacing:.09em;text-transform:uppercase;color:var(--muted)}
label.f{display:flex;flex-direction:column;gap:4px;font-size:.85rem;font-weight:500;min-width:0}
label.f .help{font-weight:400;color:var(--muted);font-size:.8rem}
label.f input,label.f textarea,.field input{padding:8px 10px;border:1px solid var(--line);border-radius:8px;background:var(--paper);font-weight:400;min-width:0}
label.f textarea{min-height:90px;resize:vertical}
textarea.tall{min-height:140px}
.actions{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.grow{flex:1}
.btn{border:1px solid var(--line);background:var(--surface);padding:8px 14px;border-radius:8px;cursor:pointer;font-weight:500}
.btn:hover{border-color:var(--muted)}
.btn.primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.btn.ghost{background:none;border-color:transparent;color:var(--muted);padding:6px 8px}
.btn.ghost:hover{color:var(--ink)}
.btn.danger{color:var(--danger)}
.btn:disabled{opacity:.5;cursor:not-allowed}
.status{font-size:.85rem;color:var(--muted)}
.status.err{color:var(--danger)} .status.ok{color:var(--ok)}
a.btn{text-decoration:none;display:inline-flex;justify-content:center}
.btn.sso{padding:12px 16px}
.whoami{align-self:center;font-size:.85rem;color:var(--muted);padding:0 8px}
.app-foot{display:flex;justify-content:center;flex-wrap:wrap;gap:0 8px;padding:6px 16px;flex:none;border-top:1px solid var(--line);background:var(--surface);font-size:.75rem;color:var(--muted);text-align:center}dialog{border:1px solid var(--line);border-radius:var(--r);background:var(--surface);color:var(--ink);padding:18px;width:calc(100% - 32px);max-width:360px}
dialog::backdrop{background:rgba(0,0,0,.35)}
dialog .stack{margin-top:0}
dialog.wide{max-width:760px}
.mat-text{white-space:pre-wrap;overflow-wrap:anywhere;max-height:60vh;overflow:auto;border:1px solid var(--line);border-radius:8px;padding:12px;background:var(--paper);font-size:.9rem}
.linkish{border:none;background:none;padding:0;text-align:left;color:var(--accent);cursor:pointer;font:inherit}
.linkish:hover{text-decoration:underline}
.field{display:flex;gap:6px;align-items:center}
.field input{flex:1}

.rail{width:250px;flex:none;border-right:1px solid var(--line);overflow:auto;padding:14px 10px;display:flex;flex-direction:column;gap:6px;background:var(--surface)}
.rail .label{padding:0 6px}
.course-btn{width:100%;text-align:left;border:1px solid transparent;background:none;border-radius:8px;padding:8px 10px;cursor:pointer;display:flex;flex-direction:column;gap:1px}
.course-btn:hover{background:var(--student)}
.course-btn[aria-current="true"]{background:var(--accent-soft);border-color:var(--line)}
.course-btn b{font-family:var(--f-mono);font-size:.78rem;font-weight:500;color:var(--accent)}
.empty{color:var(--muted);font-size:.9rem;padding:8px 6px}
.join{margin-top:auto;padding:12px 6px 0;border-top:1px solid var(--line);display:flex;flex-direction:column;gap:6px}

.dialogue{flex:1;min-width:0;display:flex;flex-direction:column;min-height:0}
.course-head{display:flex;align-items:center;gap:12px;flex-wrap:wrap;padding:12px 20px;border-bottom:1px solid var(--line)}
.course-head h2{font-size:1.25rem}
.course-head .meta{font-size:.82rem;color:var(--muted)}
.spacer{flex:1}
.ladder{display:flex;align-items:center;gap:8px;font-family:var(--f-mono);font-size:.72rem;color:var(--muted)}
.rungs{display:flex;gap:3px;align-items:flex-end}
.rung{width:10px;border-radius:2px;background:var(--line)}
.rung:nth-child(1){height:6px}.rung:nth-child(2){height:10px}.rung:nth-child(3){height:14px}.rung:nth-child(4){height:18px}
.rung.on{background:var(--mark)}
.rung.locked{background:transparent;border:1px dashed var(--line)}
.stream{flex:1;overflow:auto;padding:20px;display:flex;flex-direction:column;gap:14px}
.msg{max-width:68ch;display:flex;flex-direction:column;gap:4px}
.msg .who{font-family:var(--f-mono);font-size:.68rem;letter-spacing:.08em;text-transform:uppercase;color:var(--muted)}
.msg .body{white-space:pre-wrap;overflow-wrap:anywhere}
.msg.coach .body{font-family:var(--f-display);font-size:1.06rem;line-height:1.55}
.msg.student{align-self:flex-end}
.msg.student .body{background:var(--student);padding:10px 14px;border-radius:14px 14px 4px 14px}
.msg.student .who{text-align:right}
.msg .foot{display:flex;flex-wrap:wrap;gap:6px}
.chip{font-family:var(--f-mono);font-size:.68rem;padding:2px 7px;border-radius:999px;border:1px solid var(--line);color:var(--muted)}
.chip.hint{background:var(--mark-soft);border-color:transparent;color:var(--ink)}
.fb{display:flex;flex-direction:column;gap:6px;margin-top:2px}
.fb-row{display:flex;align-items:center;gap:4px}
.fb-btn{border:1px solid transparent;background:none;border-radius:6px;padding:2px 6px;cursor:pointer;font-size:.9rem;opacity:.8}
.fb-btn:hover{opacity:1}
.fb-btn[aria-pressed="true"]{opacity:1;background:var(--accent-soft);border-color:var(--line)}
.fb-status{font-size:.8rem;color:var(--muted);margin-left:4px}
.fb-status.err{color:var(--danger)}
.fb-why{border:1px solid var(--line);border-radius:8px;padding:10px 12px;background:var(--surface);display:flex;flex-direction:column;gap:8px;font-family:var(--f-ui);max-width:52ch}
.fb-why fieldset{border:none;padding:0}
.fb-why legend{padding:0;margin-bottom:4px}
.msg.note .body{font-size:.88rem;color:var(--muted);border-left:3px solid var(--mark);padding-left:10px}
.thinking{color:var(--muted);font-style:italic}
.composer{border-top:1px solid var(--line);padding:12px 16px;display:flex;flex-direction:column;gap:8px;background:var(--surface)}
.composer .row{display:flex;gap:8px;align-items:flex-end}
.composer textarea{flex:1;min-width:0;resize:none;min-height:44px;max-height:180px;padding:10px 12px;border:1px solid var(--line);border-radius:var(--r);background:var(--paper)}
.aux{display:flex;gap:8px;flex-wrap:wrap;align-items:center;font-size:.8rem;color:var(--muted)}
.welcome{margin:auto;max-width:52ch;display:flex;flex-direction:column;gap:10px;padding:20px}
.welcome h2{font-size:1.6rem}

.notebook{width:300px;flex:none;border-left:1px solid var(--line);overflow:auto;padding:16px;display:flex;flex-direction:column;gap:14px;background:var(--surface)}
.nb-head{display:flex;align-items:center;gap:8px}
.nb-head h3{flex:1;font-size:1.05rem}
.nb-sec{display:flex;flex-direction:column;gap:6px}
.nb-list{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:4px}
.nb-list li{display:flex;gap:6px;align-items:flex-start;font-size:.88rem;padding:4px 0;border-bottom:1px dashed var(--line)}
.nb-list li span{flex:1;min-width:0}
.x{border:none;background:none;color:var(--muted);cursor:pointer;padding:0 4px;font-size:1rem;line-height:1}
.x:hover{color:var(--danger)}
.nb-toggle{display:none}

.fac{flex:1;overflow:auto;padding:20px 16px}
.fac-inner{max-width:1080px;margin:0 auto;display:grid;grid-template-columns:240px 1fr;gap:24px;align-items:start}
.fac-main{display:flex;flex-direction:column;gap:16px;min-width:0}
.fac h2{font-size:1.4rem}
.fac h3{font-size:1.1rem}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:12px}
fieldset{border:1px solid var(--line);border-radius:8px;padding:10px 12px;margin:0;display:flex;flex-direction:column;gap:6px;min-width:0}
legend{font-size:.85rem;font-weight:500;padding:0 4px}
.radio{display:flex;gap:8px;align-items:flex-start;font-size:.88rem}
.radio small{color:var(--muted)}
.code{font-family:var(--f-mono);font-size:1.3rem;letter-spacing:.08em;background:var(--mark-soft);padding:4px 12px;border-radius:6px}
.drop{border:2px dashed var(--line);border-radius:var(--r);padding:18px;text-align:center;color:var(--muted);cursor:pointer}
.drop.over{border-color:var(--accent);background:var(--accent-soft)}
details summary{cursor:pointer;font-size:.9rem}
.stack{display:flex;flex-direction:column;gap:8px;margin-top:10px}
.mat-list{list-style:none;margin:0;padding:0}
.mat-list li{display:flex;gap:10px;align-items:center;padding:8px 0;border-bottom:1px solid var(--line);font-size:.9rem}
.mat-list .n{flex:1;min-width:0;overflow-wrap:anywhere}
.num.ended{color:var(--danger)}
.mat-list .c,.num{font-family:var(--f-mono);font-size:.75rem;color:var(--muted);font-variant-numeric:tabular-nums}
.stats{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}
.stat b{display:block;font-family:var(--f-display);font-size:1.6rem;font-variant-numeric:tabular-nums}
.stat span{font-size:.8rem;color:var(--muted)}
.bars{display:flex;flex-direction:column;gap:6px;margin-top:8px}
.bar{display:grid;grid-template-columns:150px 1fr 40px;gap:8px;align-items:center;font-size:.85rem}
.bar i{display:block;height:8px;border-radius:4px;background:var(--accent)}

@media (max-width:1000px){
  .notebook{position:fixed;right:0;top:0;bottom:0;z-index:5;box-shadow:-8px 0 24px rgba(0,0,0,.15);transform:translateX(100%);transition:transform .2s}
  .notebook.open{transform:none}
  .nb-toggle{display:inline-flex}
}
@media (max-width:760px){
  #view-coach.on{flex-direction:column}
  .rail{width:auto;border-right:none;border-bottom:1px solid var(--line);max-height:38vh}
  .fac-inner,.grid2{grid-template-columns:1fr}
  .stats{grid-template-columns:1fr 1fr}
  .bar{grid-template-columns:100px 1fr 32px}
  .stream{padding:16px}
}
@media (prefers-reduced-motion:reduce){.notebook{transition:none}}