:root {
  color-scheme: light;
  --bg: #f6f4ef;
  --panel: #ffffff;
  --ink: #202124;
  --muted: #667085;
  --line: #e3ded4;
  --accent: #6f4e37;
  --accent-dark: #513726;
  --soft: #f1ece3;
  --error: #8a1f11;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--ink);
}

.page-shell { max-width: 1280px; margin: 0 auto; padding: 28px; }
.hero { display: flex; justify-content: space-between; gap: 20px; align-items: flex-start; margin-bottom: 22px; }
.eyebrow { text-transform: uppercase; letter-spacing: .08em; color: var(--accent); font-weight: 700; font-size: 0.78rem; margin: 0 0 4px; }
h1 { font-size: clamp(2rem, 4vw, 3.4rem); margin: 0 0 8px; line-height: 1; }
h2 { margin: 0; font-size: 1.25rem; }
.subtitle { color: var(--muted); max-width: 760px; margin: 0; font-size: 1.05rem; }
.status-card { background: var(--panel); border: 1px solid var(--line); border-radius: 18px; padding: 14px 16px; min-width: 210px; box-shadow: 0 10px 24px rgba(32, 33, 36, .06); }
.dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%; background: #2e7d32; margin-right: 8px; }

.control-panel { display: grid; grid-template-columns: 1fr 1fr auto; gap: 14px; background: var(--panel); border: 1px solid var(--line); border-radius: 22px; padding: 18px; margin-bottom: 18px; box-shadow: 0 10px 24px rgba(32, 33, 36, .05); }
label { display: grid; gap: 8px; color: var(--muted); font-weight: 700; font-size: .9rem; }
select, textarea, button { font: inherit; }
select, textarea { width: 100%; border: 1px solid var(--line); border-radius: 14px; padding: 12px; background: #fff; color: var(--ink); }
button { border: 0; border-radius: 14px; padding: 12px 18px; background: var(--accent); color: white; font-weight: 800; cursor: pointer; align-self: end; }
button:hover { background: var(--accent-dark); }

.workspace { display: grid; grid-template-columns: minmax(0, 1.45fr) minmax(340px, .75fr); gap: 18px; align-items: start; }
.lesson-card, .chat-card { background: var(--panel); border: 1px solid var(--line); border-radius: 24px; box-shadow: 0 10px 24px rgba(32, 33, 36, .06); overflow: hidden; }
.section-header { padding: 18px 20px; border-bottom: 1px solid var(--line); background: linear-gradient(180deg, #fff, var(--soft)); }
.markdown-content { padding: 22px; line-height: 1.62; }
.markdown-content h1 { font-size: 2rem; }
.markdown-content h2 { margin-top: 1.5rem; }
.markdown-content code { font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace; background: #f3f4f6; padding: .15rem .3rem; border-radius: .3rem; }
.markdown-content pre { overflow-x: auto; background: #16181d; color: #f7f7f7; padding: 16px; border-radius: 16px; line-height: 1.45; }
.markdown-content pre code { background: transparent; padding: 0; color: inherit; }

.chat-card { position: sticky; top: 18px; }
.chat-log { height: 440px; overflow-y: auto; padding: 18px; display: grid; gap: 12px; background: #fbfaf7; }
.chat-message { padding: 13px 14px; border-radius: 16px; border: 1px solid var(--line); background: white; }
.chat-message.user { background: #efe8dc; }
.chat-message strong { display: block; margin-bottom: 5px; }
.chat-message p { margin: 0; color: #30343b; }
.chat-form { display: grid; gap: 10px; padding: 16px; border-top: 1px solid var(--line); }
.small-note { color: var(--muted); font-size: .86rem; padding: 0 16px 16px; margin: 0; }
.error-box { border: 1px solid #f1b9ae; background: #fff3f0; color: var(--error); padding: 14px; border-radius: 14px; }

@media (max-width: 900px) {
  .hero, .workspace { grid-template-columns: 1fr; display: grid; }
  .control-panel { grid-template-columns: 1fr; }
  .chat-card { position: static; }
}