:root {
  color-scheme: dark;

  --bg: #0b0c10;
  --fg: #f7f7fb;
  --muted: rgba(247, 247, 251, 0.86);
  --line: rgba(247, 247, 251, 0.18);
  --focus: #60a5fa;

  /* Colorblind-friendly pairing (blue/orange), but never relied on alone. */
  --ready: #3b82f6;
  --preparing: #f59e0b;

  --pad: 1.25rem;

  /* Used by JS to keep the simulation within visible capacity. */
  --ready-slots: 15;
  --prep-slots: 24;
}

@media (min-width: 1200px) {
  :root {
    --pad: 2rem;
  }
}

@media (prefers-color-scheme: light) {
  :root {
    color-scheme: light;
    --bg: #ffffff;
    --fg: #0b0c10;
    --muted: rgba(11, 12, 16, 0.78);
    --line: rgba(11, 12, 16, 0.18);
  }
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  min-height: 100svh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--fg);
  font-family:
    ui-sans-serif,
    system-ui,
    -apple-system,
    Segoe UI,
    Roboto,
    Helvetica,
    Arial;
}

.skip-link {
  position: absolute;
  left: var(--pad);
  top: var(--pad);
  padding: 0.6rem 0.75rem;
  border-radius: 0.6rem;
  border: 1px solid var(--line);
  background: var(--bg);
  color: var(--fg);
  text-decoration: none;
  transform: translateY(-180%);
}

.skip-link:focus {
  transform: translateY(0);
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: var(--pad);
  border-bottom: 1px solid var(--line);
}

.title {
  margin: 0;
  font-size: clamp(1.35rem, 1.05rem + 1vw, 2.2rem);
  letter-spacing: 0.04em;
}

.controls {
  display: flex;
  gap: 0.6rem;
}

.btn {
  appearance: none;
  cursor: pointer;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--fg);
  padding: 0.6rem 0.85rem;
  border-radius: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  font-size: 1rem;
}

.btn--secondary {
  color: var(--muted);
}

.btn:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

.board {
  flex: 1;
  min-height: 0;
  display: grid;
  grid-template-columns: 1.25fr 1fr;
}

.column {
  padding: var(--pad);
  min-height: 0;
  display: flex;
  flex-direction: column;
}

.column--ready {
  border-right: 1px solid var(--line);
}

.column__title {
  margin: 0 0 1rem;
  padding-bottom: 0.65rem;
  font-size: clamp(1.05rem, 0.85rem + 0.9vw, 1.8rem);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  border-bottom: 2px solid var(--line);
}

.column--ready .column__title {
  border-bottom-color: var(--ready);
}

.column--preparing .column__title {
  border-bottom-color: var(--preparing);
}

.codes {
  list-style: none;
  padding: 0;
  margin: 0;
  flex: 1;
  min-height: 0;
  display: grid;
  gap: 0.85rem;
  align-content: stretch;
}

.codes--ready {
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(5, 1fr);
}

.codes--preparing {
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(8, 1fr);
}

.code {
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-weight: 850;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.11em;
  line-height: 1;
  user-select: none;
}

.codes--ready .code {
  font-size: clamp(3rem, 3.6vw, 7rem);
}

.codes--preparing .code {
  font-size: clamp(1.9rem, 2.2vw, 3.8rem);
  color: var(--muted);
}

.code--empty {
  visibility: hidden;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 900px) {
  :root {
    --ready-slots: 12;
    --prep-slots: 15;
  }

  .board {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr 1fr;
  }

  .column--ready {
    border-right: none;
    border-bottom: 1px solid var(--line);
  }

  .codes--ready {
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(4, 1fr);
  }

  .codes--preparing {
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(5, 1fr);
  }
}

@media (prefers-contrast: more) {
  :root {
    --line: rgba(247, 247, 251, 0.34);
  }

  .codes--preparing .code {
    color: var(--fg);
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    scroll-behavior: auto !important;
    transition-duration: 0.001ms !important;
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
  }
}