:root {
  --bg: #fafaf7;
  --fg: #1c1c1a;
  --muted: #6b6b66;
  --border: #d9d7cf;
  --accent: #2b5cb8;
  --accent-fg: #ffffff;
  --go-valid-bg: #0f857a;   /* "Valid" — nothing marked */
  --go-submit-bg: #6d4ac0;  /* "Submit" — interests marked */
  --go-fg: #ffffff;
  --void-bg: #fde2e2;
  --void-border: #c0392b;
  --correct: #1f7a3a;
  --correct-bg: #e3f5ea;
  --correct-border: #b9e0c8;
  --incorrect: #b03030;
  --incorrect-bg: #fbe5e5;
  --incorrect-border: #e9b8b8;
  --locked-bg: #efece4;
  --surface: #ffffff;
  --disabled-bg: #cfd6e4;
  --disabled-fg: #6b6b66;
  --tap: 44px;
  color-scheme: light;
}

:root[data-theme="dark"] {
  --bg: #15161a;
  --fg: #e8e8e3;
  --muted: #9b9b94;
  --border: #383942;
  --accent: #7aa2ff;
  --accent-fg: #0f1117;
  --go-valid-bg: #15998c;
  --go-submit-bg: #8268d6;
  --go-fg: #ffffff;
  --void-bg: #4a1f1f;
  --void-border: #d9786e;
  --correct: #6fce97;
  --correct-bg: #16331f;
  --correct-border: #2c5e3d;
  --incorrect: #f08a84;
  --incorrect-bg: #3a1f1f;
  --incorrect-border: #6f3636;
  --locked-bg: #212229;
  --surface: #1d1e23;
  --disabled-bg: #2a2b31;
  --disabled-fg: #76777e;
  color-scheme: dark;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 17px;
  line-height: 1.5;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 16px 16px 64px;
}

/* Stats bar */
.stats {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.stat {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
  min-width: 60px;
}
.stat-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
}
.stat-value {
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  font-size: 16px;
}
.reset {
  margin-left: 8px;
  min-height: 36px;
  padding: 6px 12px;
  background: transparent;
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  font: inherit;
}
/* Theme toggle sits at the right edge; Reset follows it. */
#btn-theme {
  margin-left: auto;
  min-width: 44px;
  font-size: 16px;
  line-height: 1;
}

/* Prompt */
.prompt {
  color: var(--muted);
  font-size: 14px;
  margin: 8px 0 16px;
}

/* Conveyance — readable serif body */
.conveyance {
  font-family: Georgia, "Times New Roman", serif;
  font-size: 22px;
  line-height: 1.6;
  margin: 16px 0 24px;
}

/* Interest spans (rendered as <button>) */
.interest {
  font: inherit;
  color: inherit;
  background: transparent;
  border: 1px dashed var(--border);
  border-radius: 4px;
  padding: 2px 6px;
  margin: 0 1px;
  min-height: var(--tap);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}
.interest:hover { border-color: var(--accent); }
.interest:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.interest.marked {
  background: var(--void-bg);
  border: 1px solid var(--void-border);
  border-style: solid;
  text-decoration: line-through;
  text-decoration-thickness: 2px;
}

.interest.locked {
  cursor: default;
  background: var(--locked-bg);
  border-style: solid;
}
.interest.locked.marked {
  background: var(--void-bg);
}

/* Controls */
.controls {
  display: flex;
  justify-content: center;
  gap: 10px;
  margin: 16px 0;
}
.controls button,
.next,
#btn-explain {
  min-height: var(--tap);
  padding: 10px 18px;
  font: inherit;
  font-weight: 600;
  border-radius: 8px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: var(--accent-fg);
  cursor: pointer;
}
.controls button:disabled {
  background: var(--disabled-bg);
  border-color: var(--disabled-bg);
  color: var(--disabled-fg);
  cursor: not-allowed;
}
/* The single submission button: its own color, and it shifts hue Valid -> Submit. */
#btn-go {
  min-width: 160px;
  background: var(--go-valid-bg);
  border-color: var(--go-valid-bg);
  color: var(--go-fg);
  transition: background-color 0.15s ease, border-color 0.15s ease;
}
#btn-go.is-submit {
  background: var(--go-submit-bg);
  border-color: var(--go-submit-bg);
}

#btn-explain {
  background: transparent;
  color: var(--accent);
  margin-top: 8px;
}
.next { margin-top: 12px; }

/* Result */
.result { margin-top: 16px; }
.result-banner {
  font-weight: 700;
  font-size: 18px;
  padding: 10px 12px;
  border-radius: 6px;
}
.result-banner.correct {
  background: var(--correct-bg);
  color: var(--correct);
  border: 1px solid var(--correct-border);
}
.result-banner.incorrect {
  background: var(--incorrect-bg);
  color: var(--incorrect);
  border: 1px solid var(--incorrect-border);
}
.explanation {
  margin-top: 10px;
  padding: 12px 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
}
.explanation p { margin: 0 0 10px; }
.explanation p:last-child { margin: 0; }

/* Error / loading */
.error {
  margin: 16px 0;
  padding: 12px 14px;
  background: var(--incorrect-bg);
  color: var(--incorrect);
  border: 1px solid var(--incorrect-border);
  border-radius: 6px;
  white-space: pre-wrap;
}
.loading { color: var(--muted); }

@media (max-width: 480px) {
  .conveyance { font-size: 19px; }
  .stats { gap: 8px; padding: 8px 12px; }
  main { padding: 12px 12px 64px; }
}