/* Sorting Visualizer: dark theme, mobile first. */

:root {
  color-scheme: dark;
  --bg: #0f172a;
  --surface: #1e293b;
  --surface-raised: #273449;
  --surface-hover: #314158;
  --inset: rgba(15, 23, 42, 0.55);
  --border: rgba(148, 163, 184, 0.14);
  --border-strong: rgba(148, 163, 184, 0.3);
  --text: #e2e8f0;
  --text-soft: #cbd5e1;
  --muted: #94a3b8;
  --accent: #6366f1;
  --accent-hover: #7375f4;
  --accent-light: #a5b4fc;
  --accent-soft: rgba(99, 102, 241, 0.16);

  /* Bar colors, read by the canvas chart: base at the bottom, "-top" at the top of the plot. */
  --bar: #6366f1;
  --bar-top: #a5b4fc;
  --sorted: #10b981;
  --sorted-top: #6ee7b7;
  --compare: #f59e0b;
  --compare-top: #fde68a;
  --swap: #f43f5e;
  --swap-top: #fda4af;
  --write: #0ea5e9;
  --write-top: #7dd3fc;

  --radius: 12px;
  --radius-sm: 10px;
  --shadow: 0 1px 2px rgba(2, 6, 23, 0.3), 0 14px 34px -14px rgba(2, 6, 23, 0.7);
  --ease: cubic-bezier(0.2, 0.7, 0.2, 1);
  --fast: 150ms;
  --slow: 250ms;
  --font: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, 'Cascadia Mono', Menlo, Consolas, monospace;
  --gutter: 16px;
  --page-max: 1240px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  background:
    radial-gradient(900px 480px at 0% -8%, rgba(99, 102, 241, 0.16), transparent 70%),
    radial-gradient(700px 420px at 100% 0%, rgba(16, 185, 129, 0.06), transparent 70%),
    var(--bg);
  color: var(--text);
  font: 15px/1.5 var(--font);
  -webkit-font-smoothing: antialiased;
}

button,
select,
input {
  font: inherit;
  color: inherit;
}

[hidden] {
  display: none !important;
}

:focus-visible {
  outline: 2px solid var(--accent-light);
  outline-offset: 2px;
}

/* ---------- page frame ---------- */

.topbar,
.layout,
.footer {
  width: 100%;
  max-width: var(--page-max);
  margin-inline: auto;
  padding-left: max(var(--gutter), env(safe-area-inset-left));
  padding-right: max(var(--gutter), env(safe-area-inset-right));
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding-top: max(12px, env(safe-area-inset-top));
  padding-bottom: 12px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 0;
}

.brand-mark {
  width: 32px;
  height: 32px;
  flex: none;
  filter: drop-shadow(0 6px 14px rgba(99, 102, 241, 0.45));
}

.brand-title {
  margin: 0;
  font-size: clamp(16px, 4.2vw, 20px);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.01em;
}

.topbar-actions {
  display: flex;
  gap: 8px;
  flex: none;
}

.icon-btn {
  display: inline-grid;
  place-items: center;
  min-width: 42px;
  height: 42px;
  padding: 0 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.06em;
  cursor: pointer;
  touch-action: manipulation;
  transition:
    background-color var(--fast) var(--ease),
    border-color var(--fast) var(--ease),
    color var(--fast) var(--ease);
}

.icon-btn:hover {
  background: var(--surface-raised);
  border-color: var(--border-strong);
}

.icon-btn[aria-pressed='true'] {
  background: var(--accent-soft);
  border-color: rgba(129, 140, 248, 0.55);
  color: #c7d2fe;
}

.icon {
  width: 20px;
  height: 20px;
  flex: none;
}

.layout {
  flex: 1;
  display: grid;
  gap: 16px;
  align-content: start;
  padding-bottom: 8px;
}

@media (min-width: 900px) {
  .layout {
    grid-template-columns: minmax(0, 1fr) 320px;
    align-items: start;
  }
}

.card {
  min-width: 0;
  padding: 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.025), transparent 120px), var(--surface);
  box-shadow: var(--shadow);
}

@media (min-width: 600px) {
  .card {
    padding: 16px;
  }
}

/* ---------- stage: title, counters, chart, controls ---------- */

.stage {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.stage-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.stage-title {
  margin: 0;
  min-width: 0;
  font-size: 18px;
  font-weight: 650;
  line-height: 1.3;
}

.status {
  flex: none;
  display: inline-flex;
  align-items: center;
  gap: 7px;
  margin: 0;
  padding: 4px 11px;
  border-radius: 999px;
  background: rgba(148, 163, 184, 0.12);
  color: var(--muted);
  font-size: 12.5px;
  font-weight: 600;
  transition:
    background-color var(--slow) var(--ease),
    color var(--slow) var(--ease);
}

.status::before {
  content: '';
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: currentColor;
}

.status[data-state='playing'] {
  background: var(--accent-soft);
  color: #c7d2fe;
}

.status[data-state='playing']::before {
  animation: pulse 1.2s ease-in-out infinite;
}

.status[data-state='paused'] {
  background: rgba(245, 158, 11, 0.13);
  color: #fcd34d;
}

.status[data-state='done'] {
  background: rgba(16, 185, 129, 0.14);
  color: #6ee7b7;
}

@keyframes pulse {
  50% {
    opacity: 0.3;
  }
}

.stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  margin: 0;
}

@media (min-width: 560px) {
  .stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.stat {
  min-width: 0;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--inset);
}

.stat[data-role='compare'] {
  --dot: var(--compare);
}

.stat[data-role='swap'] {
  --dot: var(--swap);
}

.stat[data-role='write'] {
  --dot: var(--write);
}

.stat[data-role='steps'] {
  --dot: var(--accent-light);
}

.stat dt {
  display: flex;
  align-items: center;
  gap: 7px;
  overflow: hidden;
  color: var(--muted);
  font-size: 12px;
  white-space: nowrap;
  text-overflow: ellipsis;
}

.stat dt::before {
  content: '';
  flex: none;
  width: 8px;
  height: 8px;
  border-radius: 2px;
  background: var(--dot);
}

.stat dd {
  margin: 1px 0 0;
  overflow: hidden;
  font-size: 18px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  line-height: 1.3;
  white-space: nowrap;
  text-overflow: ellipsis;
}

@media (min-width: 560px) {
  .stat {
    padding: 8px 12px;
  }

  .stat dd {
    font-size: 20px;
  }
}

.stat-total {
  color: var(--muted);
  font-size: 14px;
  font-weight: 500;
}

.chart-wrap {
  position: relative;
  height: clamp(190px, 36vh, 320px);
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background:
    radial-gradient(120% 90% at 50% 100%, rgba(99, 102, 241, 0.1), transparent 70%),
    var(--inset);
}

@media (min-width: 900px) {
  .chart-wrap {
    height: clamp(240px, calc(100vh - 380px), 560px);
  }
}

.chart {
  position: absolute;
  inset: 0;
  display: block;
  width: 100%;
  height: 100%;
  cursor: pointer;
  /* The chart only listens for taps, so it keeps page scrolling and just drops double-tap zoom. */
  touch-action: manipulation;
}

.progress {
  height: 4px;
  margin-top: -4px;
  overflow: hidden;
  border-radius: 999px;
  background: rgba(148, 163, 184, 0.16);
}

.progress-fill {
  width: 100%;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--accent), var(--accent-light));
  transform: scaleX(0);
  transform-origin: left center;
}

.chart-foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 6px 16px;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 14px;
  margin: 0;
  padding: 0;
  list-style: none;
  color: var(--muted);
  font-size: 12.5px;
}

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

.swatch {
  width: 10px;
  height: 10px;
  border-radius: 3px;
}

.swatch[data-role='compare'] {
  background: linear-gradient(var(--compare-top), var(--compare));
}

.swatch[data-role='swap'] {
  background: linear-gradient(var(--swap-top), var(--swap));
}

.swatch[data-role='write'] {
  background: linear-gradient(var(--write-top), var(--write));
}

.swatch[data-role='sorted'] {
  background: linear-gradient(var(--sorted-top), var(--sorted));
}

.step-text {
  min-height: 1.5em;
  margin: 0;
  color: var(--text-soft);
  font-size: 13px;
  font-variant-numeric: tabular-nums;
}

.stage-foot {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 16px;
}

.transport {
  flex: 1 1 100%;
  display: grid;
  grid-template-columns: 1fr 1fr 1.3fr 1fr;
  gap: 8px;
}

@media (min-width: 640px) {
  .transport {
    flex: 0 1 auto;
    display: flex;
  }
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-width: 0;
  min-height: 44px;
  padding: 8px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface-raised);
  font-size: 14px;
  font-weight: 600;
  line-height: 1.2;
  cursor: pointer;
  user-select: none;
  touch-action: manipulation;
  transition:
    background-color var(--fast) var(--ease),
    border-color var(--fast) var(--ease),
    box-shadow var(--slow) var(--ease),
    transform var(--fast) var(--ease);
}

.btn:hover {
  background: var(--surface-hover);
  border-color: var(--border-strong);
}

.btn:active {
  transform: translateY(1px) scale(0.98);
}

.btn-primary {
  border-color: transparent;
  background: var(--accent);
  box-shadow: 0 8px 20px -8px rgba(99, 102, 241, 0.8);
  color: #fff;
}

.btn-primary:hover {
  border-color: transparent;
  background: var(--accent-hover);
}

@media (min-width: 640px) {
  .btn {
    min-width: 104px;
  }

  .btn-primary {
    min-width: 124px;
  }
}

@media (max-width: 479px) {
  .btn {
    flex-direction: column;
    gap: 3px;
    min-height: 56px;
    padding: 6px 4px;
    font-size: 12.5px;
  }
}

.hint {
  margin: 0;
  color: var(--muted);
  font-size: 12.5px;
}

.hint-sep {
  margin: 0 4px;
  opacity: 0.6;
}

.hint-touch {
  display: none;
  flex: 1 1 100%;
  text-align: center;
}

@media (hover: none) and (pointer: coarse) {
  .hint-keys {
    display: none;
  }

  .hint-touch {
    display: block;
  }
}

kbd {
  display: inline-block;
  min-width: 22px;
  padding: 2px 6px;
  border: 1px solid var(--border-strong);
  border-bottom-width: 2px;
  border-radius: 6px;
  background: var(--surface-raised);
  color: var(--text);
  font: 600 11.5px/1.4 var(--mono);
  text-align: center;
}

/* ---------- side panels: settings and algorithm info ---------- */

.side {
  display: grid;
  gap: 16px;
  min-width: 0;
}

@media (min-width: 640px) and (max-width: 899px) {
  .side {
    grid-template-columns: 1fr 1fr;
    align-items: start;
  }
}

.panel {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.panel-title {
  margin: 0;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.field-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}

.field-label {
  font-size: 13px;
  font-weight: 600;
}

.field-value {
  color: var(--accent-light);
  font-size: 13px;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

.select {
  width: 100%;
  min-height: 42px;
  padding: 8px 38px 8px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background:
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%2394a3b8' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E")
      no-repeat right 12px center / 16px,
    var(--inset);
  font-size: 14px;
  cursor: pointer;
  appearance: none;
  transition: border-color var(--fast) var(--ease);
}

.select:hover {
  border-color: var(--border-strong);
}

.select option {
  background: var(--surface);
  color: var(--text);
}

.range {
  --fill: 50%;
  width: 100%;
  height: 40px;
  margin: 0;
  background: transparent;
  cursor: pointer;
  appearance: none;
}

.range:focus-visible {
  outline: none;
}

.range::-webkit-slider-runnable-track {
  height: 6px;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--accent) var(--fill), rgba(148, 163, 184, 0.22) var(--fill));
}

.range::-webkit-slider-thumb {
  box-sizing: border-box;
  width: 20px;
  height: 20px;
  margin-top: -7px;
  border: 4px solid var(--accent);
  border-radius: 50%;
  background: #fff;
  box-shadow: 0 2px 8px rgba(2, 6, 23, 0.5);
  appearance: none;
  transition: box-shadow var(--fast) var(--ease);
}

.range:focus-visible::-webkit-slider-thumb {
  box-shadow: 0 0 0 5px rgba(129, 140, 248, 0.4);
}

.range::-moz-range-track {
  height: 6px;
  border-radius: 999px;
  background: rgba(148, 163, 184, 0.22);
}

.range::-moz-range-progress {
  height: 6px;
  border-radius: 999px;
  background: var(--accent);
}

.range::-moz-range-thumb {
  box-sizing: border-box;
  width: 20px;
  height: 20px;
  border: 4px solid var(--accent);
  border-radius: 50%;
  background: #fff;
  box-shadow: 0 2px 8px rgba(2, 6, 23, 0.5);
}

.range:focus-visible::-moz-range-thumb {
  box-shadow: 0 0 0 5px rgba(129, 140, 248, 0.4);
}

.info-text {
  margin: 0;
  color: var(--text-soft);
  font-size: 14px;
  line-height: 1.55;
}

.complexity {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  margin: 0;
}

.complexity div {
  min-width: 0;
  padding: 7px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--inset);
}

.complexity dt {
  color: var(--muted);
  font-size: 11.5px;
}

.complexity dd {
  margin: 1px 0 0;
  overflow: hidden;
  font: 600 14px/1.35 var(--mono);
  white-space: nowrap;
  text-overflow: ellipsis;
}

.stable {
  display: flex;
  align-items: baseline;
  gap: 8px;
  margin: 0;
  color: var(--text-soft);
  font-size: 13px;
}

.stable::before {
  content: '';
  flex: none;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--sorted);
  transform: translateY(-1px);
}

.stable[data-stable='false']::before {
  background: var(--swap);
}

.symbols {
  margin: 0;
  color: var(--muted);
  font-size: 12.5px;
}

/* Desktop: tighter side panels, so the side column stays about as tall as the chart card. */
@media (min-width: 900px) {
  .panel {
    gap: 10px;
  }

  .info-text {
    font-size: 13.5px;
    line-height: 1.5;
  }
}

/* Slimmer sliders only for mouse users; touch screens keep the 40px tap height. */
@media (min-width: 900px) and (pointer: fine) {
  .range {
    height: 30px;
  }
}

/* ---------- footer ---------- */

.footer {
  padding-top: 4px;
  padding-bottom: max(12px, env(safe-area-inset-bottom));
  text-align: center;
}

/* inline-block, not inline-flex: a flex container would drop the space after "MIT ·". */
.footer-link {
  display: inline-block;
  min-height: 40px;
  padding: 10px 8px;
  color: var(--muted);
  font-size: 13px;
  text-decoration: none;
  transition: color var(--fast) var(--ease);
}

.footer-link:hover {
  color: var(--text);
}

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