:root {
  --bg: #faf8f4; --panel: #ffffff; --ink: #1d1b18; --muted: #6b665e; --line: #e2ddd3;
  --accent: #2f5d50; --accent-ink: #ffffff; --good: #2e7d4f; --good-bg: #e3f3e9;
  --bad: #a83a32; --bad-bg: #f8e3e0; --soft: #f1ede5;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #161513; --panel: #1f1d1a; --ink: #ece8e1; --muted: #a39d93; --line: #35322d;
    --accent: #7fbfa9; --accent-ink: #10201b; --good: #7fcf9c; --good-bg: #1d3326;
    --bad: #ef9a90; --bad-bg: #3a2220; --soft: #282622;
  }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--ink);
  font: 17px/1.55 system-ui, -apple-system, "Segoe UI", sans-serif; }
#layout { display: flex; min-height: 100vh; }
#stage { flex: 1; max-width: 720px; margin: 0 auto; padding: 28px 16px 64px; }
h1 { font-size: 1.6rem; line-height: 1.25; margin: 0 0 12px; }
h2 { font-size: 1.25rem; margin: 0 0 10px; }
p { margin: 0 0 12px; }
.muted { color: var(--muted); font-size: .92rem; }
.card { background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 20px; margin-bottom: 16px; }
.btn { appearance: none; border: 1px solid var(--accent); background: var(--accent); color: var(--accent-ink);
  font: inherit; font-weight: 600; padding: 10px 18px; border-radius: 8px; cursor: pointer; }
.btn.ghost { background: transparent; color: var(--accent); }
.btn.small { padding: 6px 12px; font-size: .9rem; }
.btn:disabled { opacity: .4; cursor: not-allowed; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.progress { height: 6px; background: var(--soft); border-radius: 3px; margin: 6px 0 16px; overflow: hidden; }
.progress > div { height: 100%; background: var(--accent); }
.problem { font-size: 1.35rem; text-align: center; padding: 24px 8px; background: var(--soft); border-radius: 10px; margin-bottom: 18px; overflow-x: auto; }
.answer { width: 160px; font: inherit; font-size: 1.25rem; text-align: center; padding: 8px; border: 2px solid var(--ink);
  border-radius: 8px; background: var(--panel); color: var(--ink); }
.answer.correct { border-color: var(--good); background: var(--good-bg); }
.answer.incorrect { border-color: var(--bad); background: var(--bad-bg); }
.keys button { font: inherit; padding: 6px 12px; border: 1px solid var(--line); background: var(--panel); color: var(--ink); border-radius: 6px; }
.feedback { min-height: 1.5em; margin-top: 12px; }
.feedback .ok { color: var(--good); font-weight: 700; }
.feedback .sol { color: var(--muted); font-size: .95rem; }
label.choice { display: block; padding: 10px 12px; border: 1px solid var(--line); border-radius: 8px; margin-bottom: 8px; background: var(--panel); cursor: pointer; }
label.choice input { margin-right: 8px; }
textarea, select { width: 100%; font: inherit; padding: 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--panel); color: var(--ink); }
.hidden { display: none !important; }

/* Sidebar */
#sidebar { width: 38%; max-width: 460px; border-left: 1px solid var(--line); background: var(--panel);
  position: sticky; top: 0; height: 100vh; display: flex; flex-direction: column; }
#chat { display: flex; flex-direction: column; height: 100%; }
.side-head { font-weight: 700; padding: 14px 16px; border-bottom: 1px solid var(--line); }
#chat-log { flex: 1; overflow-y: auto; padding: 12px 16px; }
.msg { padding: 8px 12px; border-radius: 10px; margin-bottom: 8px; max-width: 92%; white-space: pre-wrap; overflow-wrap: anywhere; }
.msg.user { background: var(--accent); color: var(--accent-ink); margin-left: auto; }
.msg.assistant { background: var(--soft); }
#chat-form { display: flex; gap: 8px; padding: 12px 16px; border-top: 1px solid var(--line); }
#chat-input { flex: 1; font: inherit; padding: 8px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--bg); color: var(--ink); }
#tips { padding-bottom: 16px; overflow-y: auto; }
.tip { margin: 12px 16px 0; padding: 12px; background: var(--soft); border-radius: 8px; }
.tip h4 { margin: 0 0 4px; }

/* Results */
table { border-collapse: collapse; width: 100%; font-size: .95rem; }
th, td { text-align: left; padding: 6px 8px; border-bottom: 1px solid var(--line); }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; }

@media (max-width: 820px) {
  #layout { flex-direction: column; }
  #sidebar { width: 100%; max-width: none; height: auto; max-height: 55vh; position: static; border-left: 0; border-top: 1px solid var(--line); }
  #chat { height: 55vh; }
}

/* 1–7 rating scale */
.scale { display: flex; gap: 6px; margin-top: 8px; }
.scale label { flex: 1; }
.scale input { position: absolute; opacity: 0; }
.scale span { display: block; text-align: center; padding: 10px 0; border: 1px solid var(--line); border-radius: 8px; background: var(--panel); cursor: pointer; font-weight: 600; }
.scale input:checked + span { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.scale input:focus-visible + span { outline: 2px solid var(--accent); outline-offset: 2px; }
.scale-ends { display: flex; justify-content: space-between; margin-top: 6px; color: var(--muted); font-size: .85rem; gap: 12px; }