:root { --bg: #0b0e13; --panel: #131820; --panel-2: #1a2029; --line: #262e3a; --text: #e6e9ee; --muted: #8b95a5; --accent: #5bc0eb; --ok: #6fd08c; --bad: #ff7a85; --media-bg: #000; color-scheme: dark; }
/* the course has one (dark) theme; --media-bg is the letterbox behind images and canvases, black like a reading-room monitor */
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; }
a { color: var(--accent); }
.top { display: flex; gap: 12px; align-items: center; padding: 12px 16px; border-bottom: 1px solid var(--line); font-size: 14px; color: var(--muted); }
.top a { text-decoration: none; }
.page { max-width: 760px; margin: 0 auto; padding: 16px 16px 40px; }
h1 { font-size: clamp(26px, 5vw, 36px); line-height: 1.2; margin: 16px 0 6px; }
h2 { font-size: 18px; margin: 28px 0 8px; }
.meta { color: var(--muted); margin: 0 0 12px; font-size: 14px; }
.status-badge { padding: 2px 8px; border-radius: 999px; border: 1px solid var(--line); background: var(--panel-2); font-size: 12px; }
.status-badge.checked { border-color: var(--ok); color: var(--ok); }
.goals-title { margin: 0; font-weight: 600; }
.goals { margin: 4px 0 20px; color: var(--muted); }
.text p, .text li { max-width: 68ch; }
figure { margin: 20px 0; }
figure img { width: 100%; height: auto; border-radius: 8px; border: 1px solid var(--line); background: var(--media-bg); }
figcaption { font-size: 14px; color: var(--muted); margin-top: 6px; }
.credit { font-size: 12px; }
.widget { margin: 20px 0; padding: 14px; background: var(--panel); border: 1px solid var(--line); border-radius: 12px; }
.widget svg { width: 100%; height: auto; max-height: 320px; display: block; margin: 0 auto; }
.widget .row { display: flex; flex-wrap: wrap; gap: 6px; margin: 8px 0; }
.widget .say { min-height: 3em; margin: 8px 0 0; }
.widget .band { display: block; width: 100%; margin: 4px 0; padding: 12px; border-radius: 6px; border: 1px solid var(--line); font-weight: 600; text-align: left; }
.check { margin: 20px 0; padding: 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--panel); }
.check legend { font-weight: 600; padding: 0 4px; }
.choice, .btn, .widget button { display: block; width: 100%; text-align: left; margin: 6px 0; padding: 10px 12px; border-radius: 8px; border: 1px solid var(--line); background: var(--panel-2); color: var(--text); font: inherit; cursor: pointer; }
.widget .row button { display: inline-block; width: auto; margin: 0; }
.widget button[aria-pressed="true"] { border-color: var(--accent); color: var(--accent); }
.choice:disabled { cursor: default; opacity: .85; }
.choice.right { border-color: var(--ok); }
.choice.wrong { border-color: var(--bad); }
.check-fb { margin-top: 8px; padding: 10px 12px; border-left: 3px solid var(--bad); background: var(--panel-2); border-radius: 0 8px 8px 0; }
.check-fb.ok { border-left-color: var(--ok); }
.check-fb p { margin: 4px 0; }
.cite { display: block; font-size: 12px; color: var(--muted); }
.try { margin: 20px 0; padding: 14px; border-radius: 12px; border: 1px solid var(--accent); background: rgba(91,192,235,.06); }
.try-kicker { margin: 0; font-size: 12px; letter-spacing: 1.5px; text-transform: uppercase; color: var(--accent); }
.try .btn { text-decoration: none; text-align: center; font-weight: 600; }
.keypoints { margin: 28px 0; padding: 4px 16px 8px; border-radius: 12px; background: var(--panel); border: 1px solid var(--line); }
.btn-accent { background: var(--accent); color: #06121a; border-color: var(--accent); font-weight: 700; text-align: center; }
.wide { margin-top: 24px; }
.fine { color: var(--muted); font-size: 13px; }
.foot { border-top: 1px solid var(--line); padding: 16px; color: var(--muted); font-size: 13px; text-align: center; }
[hidden] { display: none !important; }
.report-link { background: none; border: 0; color: var(--muted); font: inherit; font-size: 13px; text-decoration: underline; cursor: pointer; padding: 4px 0; margin-top: 12px; }
.report-form { margin: 8px 0; padding: 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--panel); }
.report-form select, .report-form textarea { width: 100%; margin: 4px 0 8px; background: var(--panel-2); color: var(--text); border: 1px solid var(--line); border-radius: 6px; padding: 8px; font: inherit; }
.sheet-link { display: inline-block; margin-top: 8px; font-size: 13px; }
/* differential drills (question bank, review) */
.opt { display: flex; gap: 10px; align-items: flex-start; padding: 9px 12px; margin: 6px 0; border: 1px solid var(--line); border-radius: 8px; background: var(--panel-2); cursor: pointer; }
.opt input { margin-top: 5px; }
.opt.hit { border-color: var(--ok); } .opt.miss { border-color: var(--bad); border-style: dashed; } .opt.over { border-color: var(--bad); }
.opt .tag { margin-left: auto; font-size: 12px; color: var(--muted); white-space: nowrap; }
.sign { font-size: 12px; letter-spacing: 1.5px; text-transform: uppercase; color: var(--accent); margin: 0; }
/* us-probe / us-controls widgets */
.widget .probe-map { max-width: 480px; color: var(--muted); }
.widget .probe-mark { fill: var(--accent); opacity: .5; cursor: pointer; }
.widget .probe-mark .probe-hit { fill: transparent; }
.widget .probe-mark:hover, .widget .probe-mark.on { opacity: 1; }
.widget .probe-view { margin: 12px auto 0; max-width: 360px; }
.widget .probe-slice { display: block; width: 100%; height: auto; background: var(--media-bg); border-radius: 8px; }
.widget .probe-view figcaption { display: flex; flex-wrap: wrap; gap: 8px; align-items: baseline; margin-bottom: 6px; }
.widget .probe-label { font: 500 11px ui-monospace, Menlo, monospace; letter-spacing: .06em; color: var(--text); border: 1px solid var(--line); border-radius: 999px; padding: 3px 10px; }
.widget .probe-view .fine { margin: 0; }
.widget .organs { margin: 4px 0 0; }
.widget .ctrl-canvas { display: block; width: 100%; height: auto; max-width: 640px; margin: 0 auto; background: var(--media-bg); border-radius: 8px; }
.widget .ctrl-canvas[hidden] { display: none; }
.widget .ctrl-label { font: 500 11px ui-monospace, Menlo, monospace; letter-spacing: .06em; color: var(--text); margin: 8px 0 0; }
.widget .ctrls { display: grid; gap: 8px; margin: 12px 0 8px; }
.widget .ctrls label { display: grid; grid-template-columns: 9em 1fr; gap: 8px; align-items: center; font-size: 14px; color: var(--muted); }
.widget .ctrls input[type=range] { width: 100%; accent-color: var(--accent); }