:root {
  color-scheme: light dark;
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", "Noto Sans CJK SC", "Noto Sans SC", sans-serif;
  --page-bg: #f4f6fb;
  --surface: #ffffff;
  --surface-raised: #f9faff;
  --text: #172033;
  --muted: #667085;
  --border: #d8deeb;
  --accent: #3157d5;
  --accent-hover: #2548bc;
  --accent-text: #ffffff;
  --focus: #5978e9;
  --canvas-bg: #111827;
  --canvas-grid: rgba(255, 255, 255, 0.12);
  --canvas-boundary: rgba(255, 255, 255, 0.35);
  --canvas-circle: #ffffff;
  --tile-stroke: rgba(9, 14, 25, 0.5);
  --tile-east: #ff5f78;
  --tile-west: #17caa2;
  --tile-north: #68a0ff;
  --tile-south: #ffd166;
}

@media (prefers-color-scheme: dark) {
  :root {
    --page-bg: #090d15;
    --surface: #111722;
    --surface-raised: #171e2b;
    --text: #eef2fa;
    --muted: #a4afc1;
    --border: #293346;
    --accent: #7695ff;
    --accent-hover: #8aa5ff;
    --accent-text: #0a1020;
    --focus: #9bb2ff;
    --canvas-bg: #080c13;
    --canvas-grid: rgba(255, 255, 255, 0.1);
    --canvas-boundary: rgba(255, 255, 255, 0.34);
    --canvas-circle: #f8fbff;
    --tile-stroke: rgba(0, 0, 0, 0.54);
    --tile-east: #ff6580;
    --tile-west: #1dd8ad;
    --tile-north: #73a7ff;
    --tile-south: #ffd670;
  }
}

* {
  box-sizing: border-box;
}

body {
  min-width: 320px;
  margin: 0;
  background: var(--page-bg);
  color: var(--text);
}

button,
input,
select {
  font: inherit;
}

button,
select,
input[type="range"],
input[type="checkbox"] {
  accent-color: var(--accent);
}

button:focus-visible,
select:focus-visible,
input:focus-visible,
a:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--focus) 65%, transparent);
  outline-offset: 2px;
}

a {
  color: var(--accent);
}

.page-shell {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 38px 0 46px;
}

.intro {
  max-width: 720px;
  margin-bottom: 24px;
}

.kicker {
  margin: 0 0 8px;
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1 {
  margin: 0;
  font-size: clamp(2rem, 6vw, 4.2rem);
  line-height: 1.05;
  letter-spacing: -0.045em;
}

.summary {
  max-width: 680px;
  margin: 14px 0 0;
  color: var(--muted);
  font-size: clamp(1rem, 2vw, 1.16rem);
  line-height: 1.7;
}

.demo {
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--surface);
  box-shadow: 0 18px 48px rgba(22, 34, 61, 0.09);
}

.controls {
  display: flex;
  align-items: end;
  gap: 12px 16px;
  flex-wrap: wrap;
}

.target-control {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 6px 10px;
  min-width: min(260px, 100%);
  flex: 1 1 300px;
  color: var(--muted);
  font-size: 0.88rem;
}

.target-control output {
  color: var(--text);
  font-variant-numeric: tabular-nums;
  font-weight: 700;
}

.target-control input {
  grid-column: 1 / -1;
  width: 100%;
  margin: 0;
}

.button-group {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.button,
.select-control select {
  min-height: 42px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface-raised);
  color: var(--text);
}

.button {
  padding: 8px 15px;
  cursor: pointer;
  font-weight: 650;
}

.button:hover:not(:disabled) {
  border-color: var(--accent);
}

.button:disabled {
  cursor: not-allowed;
  opacity: 0.48;
}

.button-primary {
  border-color: var(--accent);
  background: var(--accent);
  color: var(--accent-text);
}

.button-primary:hover:not(:disabled) {
  border-color: var(--accent-hover);
  background: var(--accent-hover);
}

.select-control {
  display: grid;
  gap: 5px;
  color: var(--muted);
  font-size: 0.88rem;
}

.select-control select {
  padding: 7px 32px 7px 11px;
}

.switch-control {
  display: inline-flex;
  min-height: 42px;
  align-items: center;
  gap: 8px;
  color: var(--text);
  cursor: pointer;
}

.switch-control input {
  width: 18px;
  height: 18px;
  margin: 0;
}

.status-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin: 18px 0 10px;
  font-size: 0.92rem;
}

.status-row strong {
  font-variant-numeric: tabular-nums;
}

.status-row span {
  color: var(--muted);
  text-align: right;
}

.stage {
  margin: 0;
}

#tilingCanvas {
  display: block;
  width: 100%;
  aspect-ratio: 16 / 10;
  max-height: min(68vh, 720px);
  border-radius: 12px;
  background: var(--canvas-bg);
}

.legend {
  display: flex;
  align-items: center;
  gap: 9px 16px;
  flex-wrap: wrap;
  margin-top: 12px;
  color: var(--muted);
  font-size: 0.82rem;
}

.legend span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.swatch {
  width: 14px;
  height: 9px;
  border-radius: 2px;
}

.swatch-east {
  background: var(--tile-east);
}

.swatch-west {
  background: var(--tile-west);
}

.swatch-north {
  background: var(--tile-north);
}

.swatch-south {
  background: var(--tile-south);
}

.circle-key {
  width: 18px;
  border-top: 2px dashed var(--text);
}

.phase-note {
  margin: 15px 0 0;
  line-height: 1.6;
}

.source-note {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 0.8rem;
}

@media (max-width: 680px) {
  .page-shell {
    width: min(100% - 20px, 1120px);
    padding: 24px 0 30px;
  }

  .intro {
    margin-bottom: 18px;
  }

  .demo {
    padding: 12px;
    border-radius: 14px;
  }

  .controls {
    align-items: stretch;
  }

  .target-control {
    flex-basis: 100%;
  }

  .button-group {
    flex: 1 1 100%;
  }

  .button-group .button {
    flex: 1 1 auto;
  }

  .select-control,
  .switch-control {
    flex: 1 1 auto;
  }

  .status-row {
    align-items: flex-start;
    flex-direction: column;
    gap: 3px;
  }

  .status-row span {
    text-align: left;
  }

  #tilingCanvas {
    aspect-ratio: 1 / 1;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}