:root {
  color-scheme: dark;
  --bg: #0b0e14;
  --panel: #151a24;
  --panel-2: #1d2431;
  --line: #30394a;
  --text: #f4f6fa;
  --muted: #aab4c5;
  --accent: #a9ff68;
  --accent-dark: #17280d;
  --danger: #ff7a8a;
}
* { box-sizing: border-box; }
body { margin: 0; min-height: 100vh; background: var(--bg); color: var(--text); font: 15px/1.5 system-ui, sans-serif; }
button, input { font: inherit; }
button, .report-link { border: 0; border-radius: .55rem; background: var(--accent); color: #10150c; font-weight: 700; padding: .72rem 1rem; cursor: pointer; }
button:disabled { opacity: .45; cursor: not-allowed; }
input { width: 100%; margin-top: .35rem; border: 1px solid var(--line); border-radius: .5rem; background: #0d1119; color: var(--text); padding: .7rem .75rem; }
label { display: block; margin: 1rem 0; color: var(--muted); }
h1, h2, p { margin-top: 0; }
.hidden { display: none !important; }
.eyebrow { margin-bottom: .35rem; color: var(--accent); font-size: .75rem; font-weight: 800; letter-spacing: .14em; }
.panel { border: 1px solid var(--line); border-radius: 1rem; background: var(--panel); box-shadow: 0 24px 60px #0008; }
.login-shell { display: grid; min-height: 100vh; place-items: center; padding: 1rem; }
.login-card { width: min(430px, 100%); padding: 2rem; }
.message { min-height: 1.5em; margin: .75rem 0 0; }
.error { color: var(--danger); }
.lab-shell { display: grid; grid-template-columns: minmax(330px, 420px) 1fr; min-height: 100vh; }
.instructions { height: 100vh; overflow: auto; padding: 1.4rem; border-right: 1px solid var(--line); background: var(--panel); }
.student-line, .workspace-bar { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.link-button { padding: 0; background: transparent; color: var(--muted); font-weight: 500; }
.progress { height: .45rem; margin: 1.25rem 0; overflow: hidden; border-radius: 1rem; background: #080a0f; }
.progress > span { display: block; height: 100%; background: var(--accent); transition: width .25s ease; }
.step { margin: .75rem 0; padding: 1rem; border: 1px solid var(--line); border-radius: .75rem; background: var(--panel-2); }
.step.locked { opacity: .52; }
.step.complete { border-color: #53753e; background: var(--accent-dark); }
.step h2 { margin-bottom: .45rem; font-size: 1rem; }
.step p { color: var(--muted); }
.step .status { color: var(--accent); font-weight: 700; }
.step code { color: #ffd37a; }
.report-link { display: block; margin: 1rem 0; text-align: center; text-decoration: none; }
.retention-warning { margin: 1rem 0; padding: .9rem 1rem; border: 1px solid #7c6330; border-radius: .7rem; background: #2b2413; color: #f6d98b; }
.retention-warning strong { display: block; color: #ffe6a8; }
.report-actions { margin: 1rem 0; padding: 1rem; border: 1px solid #53753e; border-radius: .75rem; background: var(--accent-dark); }
.report-actions .report-link { margin: 0 0 .75rem; }
.report-actions p { margin: 0; color: var(--muted); font-size: .9rem; }
.workspace { display: grid; grid-template-rows: auto 1fr; min-width: 0; min-height: 100vh; }
.workspace-bar { padding: .75rem 1rem; border-bottom: 1px solid var(--line); background: var(--panel); }
.workspace-bar span { color: var(--muted); }
.secondary { padding: .45rem .7rem; border: 1px solid var(--line); background: transparent; color: var(--text); }
.workspace-placeholder { display: grid; place-items: center; color: var(--muted); }
#workspace-frame { width: 100%; height: 100%; border: 0; background: #111; }
@media (max-width: 900px) {
  .lab-shell { grid-template-columns: 1fr; grid-template-rows: auto 72vh; }
  .instructions { height: auto; max-height: none; border-right: 0; border-bottom: 1px solid var(--line); }
  .workspace { min-height: 72vh; }
  .workspace-bar span { display: none; }
}