:root {
  --bg: #f3f4f7;
  --surface: #ffffff;
  --border: #e3e6ec;
  --text: #1c1f26;
  --muted: #6b7280;
  --faint: #9aa2b1;

  --accent: #4f46e5;
  --accent-dark: #4338ca;

  --compare: #f59e0b;
  --compare-bg: #fff4e0;
  --swap: #ef4444;
  --swap-bg: #fde8e8;
  --pivot: #7c3aed;
  --pivot-bg: #f1eaff;
  --sorted: #10b981;
  --sorted-bg: #e5f9f1;
  --sorted-text: #0a7a56;

  --block-bg: #eef0f4;
  --block-border: #d7dbe3;

  --font: 'Inter', sans-serif;
  --mono: 'IBM Plex Mono', monospace;
}

:root[data-theme="dark"] {
  --bg: #14161c;
  --surface: #1c1f27;
  --border: #2b2f3a;
  --text: #e7e9ee;
  --muted: #9199a8;
  --faint: #5c6373;

  --accent: #818cf8;
  --accent-dark: #6366f1;

  --compare: #f5a524;
  --compare-bg: #3a2c10;
  --swap: #f87171;
  --swap-bg: #3a1e1e;
  --pivot: #a78bfa;
  --pivot-bg: #2c2340;
  --sorted: #34d399;
  --sorted-bg: #123328;
  --sorted-text: #6ee7b7;

  --block-bg: #242833;
  --block-border: #383e4c;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  transition: background-color .18s ease, color .18s ease;
}

.page {
  max-width: 1100px;
  margin: 0 auto;
  padding: 36px 24px 60px;
}

/* ---------- Header ---------- */

.page-header { margin-bottom: 22px; }
.page-header-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.page-header h1 {
  font-size: 26px;
  font-weight: 700;
  margin: 0 0 4px;
  letter-spacing: -0.01em;
}
.page-header p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.algo-desc {
  margin: -6px 0 18px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.5;
  max-width: 720px;
}

.theme-toggle {
  display: flex;
  align-items: center;
  gap: 7px;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text);
  font-family: var(--font);
  font-size: 12.5px;
  font-weight: 600;
  padding: 8px 13px;
  border-radius: 20px;
  cursor: pointer;
  transition: all .12s ease;
  flex-shrink: 0;
}
.theme-toggle:hover { border-color: var(--accent); color: var(--accent); }
.theme-toggle svg { flex-shrink: 0; }

/* ---------- Toolbar ---------- */

.toolbar {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 18px 20px;
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  margin-bottom: 18px;
  align-items: flex-end;
}

.control {
  display: flex;
  flex-direction: column;
  gap: 7px;
  min-width: 140px;
}
.control.grow { flex: 1; min-width: 220px; }
.control.actions { min-width: unset; }

.control label {
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
}
.control label span { color: var(--accent); font-weight: 700; }

select, input[type="text"] {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 9px 10px;
  border-radius: 8px;
  font-family: var(--font);
  font-size: 13.5px;
  outline: none;
}
select:focus, input[type="text"]:focus { border-color: var(--accent); }

.pill-group { display: flex; flex-wrap: wrap; gap: 6px; }

.pill {
  font-family: var(--font);
  font-size: 12.5px;
  font-weight: 500;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--muted);
  padding: 8px 12px;
  border-radius: 8px;
  cursor: pointer;
  transition: all .12s ease;
}
.pill:hover { border-color: var(--accent); color: var(--text); }
.pill.active { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }

input[type="range"] {
  -webkit-appearance: none;
  width: 140px;
  height: 5px;
  border-radius: 3px;
  background: var(--border);
  outline: none;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  border: 2px solid #fff;
  box-shadow: 0 0 0 1px var(--accent);
}
input[type="range"]::-moz-range-thumb {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  border: 2px solid #fff;
}

.input-row { display: flex; gap: 8px; }
.input-row input[type="text"] { width: 160px; }

.btn-primary, .btn-ghost {
  font-family: var(--font);
  font-size: 13.5px;
  font-weight: 600;
  padding: 9px 16px;
  border-radius: 8px;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all .12s ease;
  white-space: nowrap;
}
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--accent-dark); }
.btn-primary:disabled { opacity: 0.45; cursor: not-allowed; }
.btn-primary.is-running { background: var(--swap); }

.btn-ghost { background: var(--surface); border-color: var(--border); color: var(--text); }
.btn-ghost:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
.btn-ghost:disabled { opacity: 0.4; cursor: not-allowed; }

/* ---------- Stage card ---------- */

.stage-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 20px 24px 24px;
  margin-bottom: 18px;
}

.stage-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 18px;
}

.algo-info { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.algo-info strong { font-size: 17px; font-weight: 700; }
.algo-info span { font-family: var(--mono); font-size: 12px; color: var(--muted); }

.status-badge {
  display: flex;
  align-items: center;
  gap: 7px;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--muted);
  background: var(--bg);
  border: 1px solid var(--border);
  padding: 6px 12px;
  border-radius: 20px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.status-dot {
  width: 7px; height: 7px; border-radius: 50%;
  background: var(--faint);
}
.status-dot.running { background: var(--sorted); box-shadow: 0 0 6px var(--sorted); animation: blink 1s infinite; }
.status-dot.done { background: var(--accent); box-shadow: 0 0 6px var(--accent); }
@keyframes blink { 0%, 100% { opacity: 1; } 50% { opacity: 0.35; } }

/* ---------- Blocks ---------- */

.blocks-track {
  overflow-x: auto;
  overflow-y: hidden;
  padding: 8px 4px 14px;
}

.blocks-layer {
  position: relative;
  height: 48px;
}

.index-layer {
  position: relative;
  height: 18px;
  margin-top: 8px;
}

.index-layer span {
  position: absolute;
  top: 0;
  width: 48px;
  text-align: center;
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--faint);
}

.block {
  position: absolute;
  top: 0;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  background: var(--block-bg);
  border: 1.5px solid var(--block-border);
  color: var(--text);
  font-family: var(--mono);
  font-weight: 600;
  font-size: 13px;
  transition: left 260ms cubic-bezier(.4,0,.2,1), background-color 150ms ease, border-color 150ms ease, transform 150ms ease;
}

.block.compare { background: var(--compare-bg); border-color: var(--compare); }
.block.swap { background: var(--swap-bg); border-color: var(--swap); transform: translateY(-8px); z-index: 2; }
.block.pivot { border-color: var(--pivot); box-shadow: inset 0 0 0 1.5px var(--pivot); }
.block.sorted { background: var(--sorted-bg); border-color: var(--sorted); color: var(--sorted-text); }

.block.flash {
  animation: flashIn 260ms ease;
}
@keyframes flashIn {
  from { transform: scale(0.82); opacity: 0.35; }
  to { transform: scale(1); opacity: 1; }
}

/* ---------- Legend ---------- */

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
}
.legend span {
  display: flex;
  align-items: center;
  gap: 7px;
  font-size: 12.5px;
  color: var(--muted);
}
.dot-sw { width: 11px; height: 11px; border-radius: 3px; display: inline-block; }
.dot-sw.default { background: var(--block-bg); border: 1.5px solid var(--block-border); }
.dot-sw.compare { background: var(--compare-bg); border: 1.5px solid var(--compare); }
.dot-sw.swap { background: var(--swap-bg); border: 1.5px solid var(--swap); }
.dot-sw.pivot { background: var(--pivot-bg); border: 1.5px solid var(--pivot); }
.dot-sw.sorted { background: var(--sorted-bg); border: 1.5px solid var(--sorted); }

/* ---------- Stats strip ---------- */

.stats-strip {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-bottom: 8px;
}

.stat {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 16px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.stat span { font-size: 11.5px; color: var(--muted); font-weight: 500; }
.stat b { font-family: var(--mono); font-size: 19px; font-weight: 600; }

.progress-track {
  height: 6px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 4px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  width: 0%;
  background: var(--accent);
  transition: width .1s linear;
}

/* ---------- Footer ---------- */

.page-footer {
  text-align: center;
  color: var(--faint);
  font-size: 11.5px;
  margin-top: 22px;
}

/* ---------- Responsive ---------- */

@media (max-width: 700px) {
  .stats-strip { grid-template-columns: 1fr 1fr; }
  .toolbar { padding: 16px; }
}