/* DT Classroom CAD Studio: the same frame as the immersive lessons (lesson rail, lesson card, status strip, control
   bar over a full-screen 3D scene), in the site's light paper palette with a drawing-board blue accent. */
:root{color-scheme:light;--paper:#f3efe6;--paper2:#fffdf7;--ink:#17212b;--navy:#16344c;--accent:#2463eb;--accent2:#e9f0ff;--yellow:#f3c84b;--orange:#ef7a3a;--green:#2c9b6c;--red:#c43d3d;--line:#dcd4c6;--muted:#56636d;--glass:rgba(255,253,247,.86)}
*{box-sizing:border-box}
html,body{margin:0;height:100%}
body{background:var(--paper);color:var(--ink);font:15px/1.5 Inter,system-ui,-apple-system,"Segoe UI",Arial,sans-serif}
button,input,select,textarea{font:inherit;color:inherit}button{cursor:pointer}
a{color:var(--accent)}
:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
.cad-skip{position:absolute;left:-999px;top:0;background:#fff;color:#000;padding:8px 12px;z-index:99}.cad-skip:focus{left:8px;top:8px}
.cad-app{position:fixed;inset:0;overflow:hidden}
.cad-scene{position:absolute;inset:0;background:radial-gradient(120% 90% at 62% 30%,#fbfdff 0%,#eef3f7 55%,#e6ebef 100%)}
.cad-canvas{display:block;width:100%;height:100%;touch-action:none;cursor:grab}.cad-canvas:active{cursor:grabbing}
.cad-pins{position:absolute;inset:0;pointer-events:none;overflow:hidden}
.cad-pin{position:absolute;left:0;top:0;padding:3px 7px;border-radius:6px;background:rgba(22,52,76,.9);color:#fff;font:700 11px/1.2 "JetBrains Mono",ui-monospace,monospace;white-space:nowrap;box-shadow:0 2px 8px rgba(0,0,0,.12)}
.cad-nogl{position:absolute;left:50%;top:50%;transform:translate(-30%,-50%);max-width:360px;background:#fff;border:1px solid var(--line);border-radius:12px;padding:14px 16px;color:var(--muted)}
.cad-glass{background:var(--glass);border:1px solid rgba(22,52,76,.12);box-shadow:0 16px 48px rgba(22,52,76,.12),inset 0 1px 0 #fff;backdrop-filter:blur(16px) saturate(1.1);-webkit-backdrop-filter:blur(16px) saturate(1.1);border-radius:18px}
.cad-ey{font:700 9.5px "JetBrains Mono",ui-monospace,monospace;letter-spacing:.16em;text-transform:uppercase;color:var(--accent)}

/* lesson rail */
.cad-rail{position:absolute;left:16px;top:16px;bottom:112px;width:236px;padding:12px;display:flex;flex-direction:column;gap:10px;z-index:20}
.cad-rail-head{padding:8px 8px 12px;border-bottom:1px solid var(--line)}
.cad-rail-head h1{margin:6px 0 0;font-size:20px;line-height:1.08;letter-spacing:-.02em;color:var(--navy)}
.cad-rail-head p{margin:5px 0 0;font-size:11.8px;line-height:1.45;color:var(--muted)}
.cad-back{display:block;margin-top:10px;border:1px solid var(--line);background:#fff;border-radius:10px;padding:7px 10px;font-size:12px;font-weight:700;color:var(--navy);text-decoration:none}
.cad-back:hover{border-color:var(--navy)}
.cad-lessons{display:flex;flex-direction:column;gap:3px;overflow:auto;min-height:0}
.cad-lesson{display:flex;align-items:center;gap:9px;border:1px solid transparent;background:none;border-radius:11px;padding:8px;text-align:left;color:var(--navy);text-decoration:none}
.cad-lesson:hover{background:rgba(22,52,76,.05)}
.cad-lesson[aria-current="page"]{background:var(--accent2);border-color:rgba(36,99,235,.35)}
.cad-lesson .n{width:26px;height:26px;border-radius:8px;display:grid;place-items:center;background:rgba(22,52,76,.07);color:var(--muted);font:700 10.5px "JetBrains Mono",monospace;flex:none}
.cad-lesson[aria-current="page"] .n{background:var(--accent);color:#fff}
.cad-lesson .t{font-size:12.6px;font-weight:700;line-height:1.25}
.cad-lesson .t small{display:block;font-weight:500;font-size:11px;color:var(--muted)}
.cad-lesson .tick{margin-left:auto;color:var(--green);font-weight:900}

/* status strip */
.cad-top{position:absolute;left:268px;right:16px;top:16px;z-index:20;min-height:58px;padding:10px 210px 10px 16px;display:flex;align-items:center;gap:20px}
.cad-metrics{display:flex;gap:22px;min-width:0;overflow:hidden}
.cad-metric span{display:block;font-size:9px;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);white-space:nowrap}
.cad-metric strong{display:block;margin-top:3px;font:700 12.5px/1.2 "JetBrains Mono",ui-monospace,monospace;white-space:nowrap;color:var(--navy)}
.cad-state{margin-left:auto;text-align:right}
.cad-hint{font-size:11px;color:var(--muted);white-space:nowrap}

/* lesson card */
.cad-card{position:absolute;left:268px;top:88px;width:410px;max-height:calc(100% - 196px);overflow:auto;z-index:20;padding:14px;outline:none}
.cad-card-head{display:flex;gap:11px;align-items:flex-start}
.cad-card-head .num{width:36px;height:36px;border-radius:10px;border:1px solid var(--line);background:#fff;display:grid;place-items:center;font:800 12px "JetBrains Mono",monospace;color:var(--navy);flex:none}
.cad-card h2{margin:2px 0 0;font-size:19px;line-height:1.15;letter-spacing:-.02em;color:var(--navy)}
.cad-sum{margin:10px 0 0;font-size:13px;line-height:1.5;color:#3d4954}
.cad-tabs{display:flex;gap:6px;flex-wrap:wrap;margin:12px 0 10px}
.cad-tab{border:1px solid var(--line);background:#fff;border-radius:999px;padding:5px 12px;font-size:12px;font-weight:700;color:var(--navy)}
.cad-tab[aria-selected="true"]{background:var(--navy);border-color:var(--navy);color:#fff}

/* a step, in the booklet's layout */
.cad-step-h{display:flex;align-items:stretch;border-radius:10px;overflow:hidden;border:1px solid #cfe0f5;background:#eef5ff}
.cad-step-h .lab{background:var(--accent);color:#fff;font:800 11px "JetBrains Mono",monospace;letter-spacing:.06em;padding:9px 11px;display:grid;place-items:center;white-space:nowrap}
.cad-step-h h3{margin:0;padding:8px 12px;font-size:15.5px;line-height:1.25;color:var(--navy);align-self:center}
.cad-acts{list-style:none;margin:8px 0 0;padding:0;border:1px solid var(--line);border-radius:10px;overflow:hidden;background:#fff}
.cad-acts li{display:grid;grid-template-columns:28px 38px 1fr;align-items:center;border-top:1px solid var(--line);min-height:44px}
.cad-acts li:first-child{border-top:0}
.cad-acts .i{align-self:stretch;display:grid;place-items:center;background:var(--accent);color:#fff;font:800 11px "JetBrains Mono",monospace}
.cad-acts .ic{display:grid;place-items:center;color:var(--navy)}
.cad-acts .ic svg{width:22px;height:22px}
.cad-acts .tx{padding:8px 10px 8px 2px;font-size:13px;line-height:1.5}
kbd{display:inline-block;background:#1d2a36;color:#fff;border-radius:4px;padding:0 6px;margin:0 1px;font:700 11px/1.75 "JetBrains Mono",ui-monospace,monospace;white-space:nowrap}
.cad-n{display:inline-block;background:#fff1c2;border:1px solid #ecd27a;color:#4a3b00;border-radius:4px;padding:0 6px;margin:0 1px;font:700 11.5px/1.65 "JetBrains Mono",ui-monospace,monospace;white-space:nowrap}
.cad-look{margin:10px 0 0;padding:9px 12px;border-radius:10px;background:#f0f7f2;border:1px solid #cde6d6;color:#1f5e3f;font-size:12.6px;font-weight:700}
.cad-look span{font-weight:500}
.cad-tip{margin:8px 0 0;padding:8px 12px;border-left:4px solid var(--yellow);background:#fffaf0;border-radius:0 10px 10px 0;font-size:12.6px;color:#4c4231}
.cad-predict{margin:10px 0 0;border:1px dashed #9db6dd;border-radius:10px;padding:10px 12px;background:#fbfdff}
.cad-predict b{display:block;font-size:10px;letter-spacing:.14em;text-transform:uppercase;color:var(--accent);font-family:"JetBrains Mono",monospace}
.cad-predict p{margin:5px 0 8px;font-size:13px}
.cad-predict .ans{margin:8px 0 0;padding:8px 10px;border-radius:8px;background:var(--accent2);font-size:12.8px}
.cad-btn{border:1px solid var(--line);background:#fff;border-radius:10px;padding:7px 12px;font-size:12.5px;font-weight:700;color:var(--navy)}
.cad-btn:hover{border-color:var(--navy)}
.cad-btn.primary{background:var(--navy);border-color:var(--navy);color:#fff}
.cad-btn.go{background:var(--accent);border-color:var(--accent);color:#fff}
.cad-btn[disabled]{opacity:.45;cursor:default}
.cad-stepnav{display:flex;gap:8px;align-items:center;justify-content:space-between;margin-top:12px}
.cad-stepnav small{color:var(--muted);font-size:11.5px}

/* learn / apply / check */
.cad-sec{margin-top:14px}
.cad-sec h3{margin:0 0 7px;font-size:13.5px;color:var(--navy)}
.cad-sizes{width:100%;border-collapse:collapse;font-size:12.6px;background:#fff;border:1px solid var(--line);border-radius:10px;overflow:hidden}
.cad-sizes th,.cad-sizes td{text-align:left;padding:6px 9px;border-top:1px solid var(--line);vertical-align:top}
.cad-sizes tr:first-child th,.cad-sizes tr:first-child td{border-top:0}
.cad-sizes th{width:38%;background:#f7f3ea;color:var(--navy)}
.cad-obj{margin:0;padding-left:18px;font-size:12.8px}
.cad-words{display:grid;gap:6px}
.cad-word{background:#fff;border:1px solid var(--line);border-radius:10px;padding:8px 10px;font-size:12.5px}
.cad-word b{display:block;color:var(--navy);font-size:13px}
.cad-chips{display:flex;flex-wrap:wrap;gap:6px}
.cad-chip{border:1px solid var(--line);background:#fff;border-radius:999px;padding:3px 10px;font-size:11.5px;font-weight:600;color:var(--navy)}
.cad-list{margin:0;padding-left:18px;font-size:12.8px}.cad-list li{margin:3px 0}
.cad-tools{display:grid;grid-template-columns:1fr 1fr;gap:6px}
.cad-tool{display:flex;align-items:center;gap:8px;background:#fff;border:1px solid var(--line);border-radius:10px;padding:6px 8px;font-size:12.3px}
.cad-tool svg{width:22px;height:22px;flex:none;color:var(--navy)}
.cad-tool span{flex:1;font-weight:600}
.cad-nea{background:#fff8e6;border:1px solid #f0d58c;border-radius:12px;padding:10px 12px;font-size:12.6px}
.cad-nea b{color:#6b4c00}
.cad-teacher{border:1px solid var(--line);border-radius:10px;background:#fff;padding:8px 10px;font-size:12.5px}
.cad-teacher summary{font-weight:700;color:var(--navy);cursor:pointer}
.cad-apply textarea{width:100%;min-height:150px;margin-top:8px;border:1px solid var(--line);border-radius:10px;padding:10px;background:#fff;font-size:13px;line-height:1.5;resize:vertical}
.cad-q{background:#fff;border:1px solid var(--line);border-radius:12px;padding:10px 12px;margin-top:8px}
.cad-q p{margin:0 0 8px;font-size:13px;font-weight:700;color:var(--navy)}
.cad-q .opts{display:grid;gap:5px}
.cad-q .opts button{text-align:left;border:1px solid var(--line);background:#fcfbf7;border-radius:9px;padding:7px 10px;font-size:12.6px}
.cad-q .opts button:hover:not([disabled]){border-color:var(--navy)}
.cad-q .opts button.right{background:#e7f6ee;border-color:#7cc6a0;color:#14532d;font-weight:700}
.cad-q .opts button.wrong{background:#fdecec;border-color:#e3a0a0;color:#7f1d1d}
.cad-q .why{margin:8px 0 0;font-size:12.3px;color:#3d4954}
.cad-score{margin-top:12px;padding:10px 12px;border-radius:10px;background:var(--accent2);font-weight:700;color:var(--navy);font-size:13px}
.cad-done{color:var(--green)}

/* control bar */
.cad-panel{position:absolute;left:268px;right:76px;bottom:16px;z-index:20;padding:10px 14px;display:flex;gap:10px 16px;align-items:center;flex-wrap:wrap}
.cad-dots{display:flex;gap:4px;flex-wrap:wrap;align-items:center}
.cad-dot{width:28px;height:28px;border-radius:8px;border:1px solid var(--line);background:#fff;font:700 11px "JetBrains Mono",monospace;color:var(--muted)}
.cad-dot.seen{color:var(--navy);border-color:#b9c7d6}
.cad-dot[aria-current="step"]{background:var(--accent);border-color:var(--accent);color:#fff}
.cad-seg{display:inline-flex;border:1px solid var(--line);border-radius:10px;overflow:hidden;background:#fff}
.cad-seg button{border:0;background:none;padding:6px 10px;font-size:12px;font-weight:700;color:var(--navy)}
.cad-seg button[aria-pressed="true"]{background:var(--navy);color:#fff}
.cad-panel .grow{flex:1}
.cad-mini{font:700 9px "JetBrains Mono",monospace;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin-right:2px}

/* phones and narrow windows: one column, model on top */
@media (max-width:980px){
  .cad-app{position:static;overflow:visible}
  html,body{height:auto}
  .cad-scene{position:sticky;top:0;height:42vh;min-height:240px;z-index:5;border-bottom:1px solid var(--line);box-shadow:0 6px 18px rgba(22,52,76,.08)}
  .cad-rail,.cad-top,.cad-card,.cad-panel{position:relative;left:auto;right:auto;top:auto;bottom:auto;width:auto;max-height:none;margin:10px 12px;z-index:1;backdrop-filter:none;-webkit-backdrop-filter:none}
  .cad-app{padding-bottom:96px}
  .cad-rail{display:block;padding:10px}
  .cad-rail-head{display:none}
  .cad-lessons{flex-direction:row;overflow-x:auto;padding-bottom:2px}
  .cad-lesson{flex:none}
  .cad-top{display:none}
  .cad-app{display:flex;flex-direction:column}
  .cad-scene{order:0}.cad-rail{order:1}.cad-card{order:2}.cad-panel{order:3}
}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
@media(max-width:1500px){.cad-hint{display:none}}