:root {
  color-scheme: light;
  --bg: #f3efe6;
  --panel: #fbf9f4;
  --panel-alt: #f3ede0;
  --panel-border: #e2d9c6;
  --ink: #26221c;
  --ink-dim: #7a715f;
  --accent: #b5502e;
  --accent-ink: #fdf4ed;
  --accent-soft: #f0ddd0;
  --teal: #2f6f68;
  --teal-soft: #dfe9e6;
  --danger: #a8341f;
  --danger-soft: #f3ded9;
  --warn: #93650f;
  --warn-soft: #f1e3c4;
  --shadow: 0 1px 2px rgba(38, 34, 28, 0.04), 0 6px 20px rgba(38, 34, 28, 0.05);
  --mono: "SF Mono", "JetBrains Mono", ui-monospace, Menlo, Consolas, monospace;
  --serif: ui-serif, Georgia, "Iowan Old Style", "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    color-scheme: dark;
    --bg: #1b1814;
    --panel: #242019;
    --panel-alt: #2b261e;
    --panel-border: #3c352a;
    --ink: #ede6d9;
    --ink-dim: #a49a86;
    --accent: #dc8258;
    --accent-ink: #241209;
    --accent-soft: #3a2417;
    --teal: #7fbcb2;
    --teal-soft: #223330;
    --danger: #e2836d;
    --danger-soft: #3a231d;
    --warn: #e0b968;
    --warn-soft: #362c17;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.2), 0 8px 24px rgba(0, 0, 0, 0.25);
  }
}

* { box-sizing: border-box; }

html, body { height: 100%; }

body {
  margin: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--ink);
  -webkit-font-smoothing: antialiased;
}

#app {
  display: flex;
  min-height: 100vh;
}

/* ---------------- sidebar ---------------- */
#sidebar {
  width: 260px;
  flex-shrink: 0;
  background: var(--panel);
  border-right: 1px solid var(--panel-border);
  display: flex;
  flex-direction: column;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}

.brand {
  padding: 20px 18px 14px;
  border-bottom: 1px solid var(--panel-border);
}
.brand-title {
  font-family: var(--serif);
  font-size: 22px;
  font-weight: 600;
  letter-spacing: 0.02em;
}
.brand-sub {
  font-size: 12px;
  color: var(--ink-dim);
  margin-top: 2px;
}

#module-list { padding: 10px; flex: 1; }

.mod-item {
  display: block;
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  border-radius: 8px;
  padding: 10px 10px;
  margin-bottom: 2px;
  cursor: pointer;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 13.5px;
}
.mod-item:hover { background: var(--panel-alt); }
.mod-item.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.mod-item .mod-num {
  display: inline-block;
  width: 20px;
  color: var(--ink-dim);
  font-family: var(--mono);
  font-size: 12px;
}
.mod-item.active .mod-num { color: var(--accent); }
.mod-progress {
  float: right;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--ink-dim);
}

.sidebar-footer {
  padding: 10px;
  border-top: 1px solid var(--panel-border);
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.side-link {
  display: block;
  text-align: left;
  background: none;
  border: none;
  padding: 8px 10px;
  border-radius: 8px;
  font-size: 13px;
  color: var(--ink-dim);
  cursor: pointer;
  text-decoration: none;
  font-family: var(--sans);
}
.side-link:hover { background: var(--panel-alt); color: var(--ink); }

/* ---------------- main ---------------- */
#main {
  flex: 1;
  padding: 32px 40px 80px;
  max-width: 900px;
}

.module-header h1 {
  font-family: var(--serif);
  font-size: 30px;
  margin: 0 0 4px;
}
.module-header .module-num-label {
  font-family: var(--mono);
  color: var(--accent);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.module-intro {
  margin: 18px 0 30px;
  padding: 18px 22px;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  box-shadow: var(--shadow);
  line-height: 1.65;
  font-size: 14.5px;
}
.module-intro p { margin: 0 0 12px; }
.module-intro p:last-child { margin-bottom: 0; }
.module-intro code {
  background: var(--panel-alt);
  padding: 1px 5px;
  border-radius: 4px;
  font-family: var(--mono);
  font-size: 0.9em;
}
.module-intro pre {
  background: var(--panel-alt);
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  padding: 12px 14px;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 12.5px;
  line-height: 1.5;
}
.module-intro strong { color: var(--accent); }

/* ---------------- problem card ---------------- */
.problem {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  margin-bottom: 22px;
  overflow: hidden;
}
.problem-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  padding: 16px 20px 12px;
  gap: 10px;
}
.problem-title {
  font-family: var(--serif);
  font-size: 18px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 8px;
}
.problem-title .status-dot {
  width: 9px; height: 9px; border-radius: 50%;
  background: var(--panel-border);
  flex-shrink: 0;
  display: inline-block;
}
.problem-title .status-dot.pass { background: var(--teal); }
.problem-title .status-dot.fail { background: var(--danger); }
.problem-meta {
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--ink-dim);
  white-space: nowrap;
}
.problem-body { padding: 0 20px 18px; }
.problem-prompt {
  font-size: 14px;
  line-height: 1.6;
  color: var(--ink);
  margin-bottom: 14px;
  white-space: pre-line;
}
.problem-prompt code {
  background: var(--panel-alt);
  padding: 1px 5px;
  border-radius: 4px;
  font-family: var(--mono);
  font-size: 0.9em;
}
.pill {
  display: inline-block;
  font-size: 10.5px;
  font-family: var(--mono);
  padding: 2px 8px;
  border-radius: 20px;
  background: var(--panel-alt);
  color: var(--ink-dim);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.pill.gpu { background: var(--warn-soft); color: var(--warn); }

/* written */
textarea.draft {
  width: 100%;
  min-height: 90px;
  font-family: var(--sans);
  font-size: 13.5px;
  padding: 10px 12px;
  border-radius: 8px;
  border: 1px solid var(--panel-border);
  background: var(--panel-alt);
  color: var(--ink);
  resize: vertical;
  line-height: 1.5;
}
textarea.draft:focus { outline: 2px solid var(--accent-soft); border-color: var(--accent); }

.btn-row { display: flex; gap: 8px; margin-top: 10px; flex-wrap: wrap; align-items: center; }
button.btn {
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 600;
  padding: 8px 14px;
  border-radius: 8px;
  border: 1px solid var(--panel-border);
  background: var(--panel-alt);
  color: var(--ink);
  cursor: pointer;
}
button.btn:hover { border-color: var(--accent); }
button.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
button.btn.primary:hover { opacity: 0.9; }
button.btn:disabled { opacity: 0.5; cursor: default; }
button.btn.small { padding: 5px 10px; font-size: 12px; }

.answer-box, .hint-box, .refresher-box {
  margin-top: 10px;
  padding: 12px 14px;
  border-radius: 8px;
  font-size: 13.5px;
  line-height: 1.55;
  display: none;
}
.answer-box.open, .hint-box.open, .refresher-box.open { display: block; }
.answer-box { background: var(--teal-soft); border: 1px solid var(--teal); }
.hint-box { background: var(--warn-soft); border: 1px solid var(--warn); white-space: pre-line; }
.hint-box code { background: rgba(0,0,0,0.06); padding: 1px 4px; border-radius: 4px; font-family: var(--mono); }
.refresher-box { background: var(--panel-alt); border: 1px solid var(--panel-border); white-space: pre-line; }
.refresher-box code { background: rgba(0,0,0,0.06); padding: 1px 4px; border-radius: 4px; font-family: var(--mono); }

/* code editor */
.fn-block { margin-bottom: 14px; }
.fn-name {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-dim);
  margin-bottom: 4px;
}
.CodeMirror {
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 12.5px;
  height: auto;
}
.CodeMirror-scroll { min-height: 120px; max-height: 480px; }

.result-banner {
  margin-top: 12px;
  padding: 10px 14px;
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 13px;
  display: none;
}
.result-banner.show { display: block; }
.result-banner.pass { background: var(--teal-soft); color: var(--teal); border: 1px solid var(--teal); }
.result-banner.fail { background: var(--danger-soft); color: var(--danger); border: 1px solid var(--danger); }
.result-output {
  margin-top: 8px;
  background: #1b1814;
  color: #ede6d9;
  padding: 12px;
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 11.5px;
  line-height: 1.5;
  white-space: pre-wrap;
  max-height: 320px;
  overflow-y: auto;
  display: none;
}
.result-output.show { display: block; }

/* gpu */
.gpu-config {
  background: var(--panel-alt);
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  padding: 10px 12px;
  font-family: var(--mono);
  font-size: 11.5px;
  margin-bottom: 10px;
  white-space: pre-wrap;
  color: var(--ink-dim);
}
input.cmd-input {
  width: 100%;
  font-family: var(--mono);
  font-size: 12.5px;
  padding: 8px 10px;
  border-radius: 8px;
  border: 1px solid var(--panel-border);
  background: var(--panel);
}
.gpu-row { display: flex; gap: 8px; align-items: center; margin-top: 8px; }
.gpu-row label { font-size: 12px; color: var(--ink-dim); }
input.timeout-input { width: 60px; font-family: var(--mono); padding: 6px; border-radius: 6px; border: 1px solid var(--panel-border); }
.gpu-log {
  margin-top: 10px;
  background: #1b1814;
  color: #ede6d9;
  padding: 12px;
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 11.5px;
  line-height: 1.5;
  white-space: pre-wrap;
  max-height: 360px;
  overflow-y: auto;
  display: none;
}
.gpu-log.show { display: block; }
.gpu-status { font-family: var(--mono); font-size: 12px; margin-top: 6px; }
.deliverables { margin: 8px 0 0; padding-left: 18px; font-size: 13px; color: var(--ink-dim); }
.deliverables li { margin-bottom: 3px; }

/* shared code / gpu history modal-ish full page */
.panel-page {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  padding: 20px 24px;
}
.panel-page h2 { font-family: var(--serif); margin-top: 0; }
.panel-page p.help { color: var(--ink-dim); font-size: 13px; }

.run-entry {
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  padding: 12px 14px;
  margin-bottom: 10px;
  background: var(--panel-alt);
}
.run-entry-head { display: flex; justify-content: space-between; font-family: var(--mono); font-size: 12px; }
.run-status { text-transform: uppercase; font-weight: 700; }
.run-status.running { color: var(--warn); }
.run-status.completed { color: var(--teal); }
.run-status.failed { color: var(--danger); }

.toggle-row { display: flex; gap: 6px; flex-wrap: wrap; }

::selection { background: var(--accent-soft); }

@media (max-width: 800px) {
  #app { flex-direction: column; }
  #sidebar { position: relative; width: 100%; height: auto; }
  #main { padding: 20px; max-width: 100%; }
}