:root {
  color-scheme: dark;
  --bg: #0f172a;
  --surface: #1e293b;
  --surface-raised: #26344b;
  --surface-hover: #2c3b54;
  --border: #334155;
  --border-soft: #233047;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --accent: #0ea5e9;
  --accent-bright: #38bdf8;
  --accent-ink: #04121c;
  --accent-soft: rgba(14, 165, 233, 0.16);
  --good: #4ade80;
  --warn: #fbbf24;
  --bad: #fb7185;
  --radius: 12px;
  --shadow: 0 12px 32px -16px rgba(2, 6, 23, 0.8), 0 2px 6px rgba(2, 6, 23, 0.35);
  --speed: 200ms;
  --ease: cubic-bezier(0.2, 0.7, 0.3, 1);
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;

  /* Board palette: read by the canvas renderer and shared with the legend. */
  --board-gap: #0b1222;
  --cell-empty: #1a2539;
  --cell-wall: #4b5a73;
  --cell-weight: #3b1f70;
  --cell-weight-icon: #c4b5fd;
  --cell-frontier: #38bdf8;
  --cell-visited: #0b4f78;
  --cell-path-fill: #854d0e;
  --cell-path: #facc15;
  --cell-path-glow: rgba(250, 204, 21, 0.55);
  --cell-start: #16a34a;
  --cell-end: #e11d48;
  --cell-glyph: #f8fafc;
  --cell-hover: rgba(226, 232, 240, 0.55);

  /* Viewport height without the browser's bars (svh) where supported, else vh. A var()
     holding a unit the browser cannot parse would void every height built on it. */
  --viewport-height: 100vh;
  /* The board's height depends on the viewport only, never on the page content. */
  --board-height: clamp(240px, calc(var(--viewport-height) - 300px), 560px);
}

@supports (height: 100svh) {
  :root {
    --viewport-height: 100svh;
  }
}

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

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

body {
  margin: 0;
  min-height: var(--viewport-height);
  display: flex;
  flex-direction: column;
  background:
    radial-gradient(1100px 520px at 12% -12%, rgba(14, 165, 233, 0.12), transparent 62%),
    radial-gradient(900px 480px at 100% 0%, rgba(124, 58, 237, 0.08), transparent 60%),
    var(--bg);
  color: var(--text);
  font: 400 15px/1.5 var(--font);
  overflow-x: hidden;
}

h1,
h2,
h3,
p {
  margin: 0;
}

a {
  color: var(--accent-bright);
  text-underline-offset: 3px;
}

kbd {
  display: inline-block;
  min-width: 1.9em;
  padding: 1px 7px;
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 6px;
  background: var(--surface-raised);
  color: var(--text);
  font: 600 0.78rem/1.6 var(--font);
  text-align: center;
  white-space: nowrap;
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* Header and footer */

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 16px;
  border-bottom: 1px solid var(--border-soft);
  background: rgba(15, 23, 42, 0.72);
}

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

.logo {
  width: 32px;
  height: 32px;
  flex: none;
  filter: drop-shadow(0 4px 10px rgba(14, 165, 233, 0.35));
}

.brand h1 {
  font-size: clamp(1.05rem, 0.92rem + 0.7vw, 1.4rem);
  font-weight: 750;
  line-height: 1.15;
  letter-spacing: -0.015em;
}

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

.app-footer {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 8px;
  padding: 6px 16px 10px;
  color: var(--muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border-soft);
}

.app-footer a {
  display: inline-block;
  padding: 10px 2px;
}

/* Buttons and form controls */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 44px;
  min-width: 44px;
  padding: 0 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface-raised);
  color: var(--text);
  font: 600 0.95rem/1.2 var(--font);
  white-space: nowrap;
  cursor: pointer;
  transition:
    background-color var(--speed) var(--ease),
    border-color var(--speed) var(--ease),
    color var(--speed) var(--ease),
    box-shadow var(--speed) var(--ease),
    transform 150ms var(--ease);
}

.btn:hover {
  background: var(--surface-hover);
  border-color: #475569;
}

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

.btn:focus-visible,
select:focus-visible,
summary:focus-visible,
.app-footer a:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.btn-quiet {
  background: transparent;
}

.btn-lang {
  padding: 0 12px;
  letter-spacing: 0.06em;
}

.icon {
  width: 18px;
  height: 18px;
  flex: none;
  fill: currentColor;
}

.btn-quiet .icon {
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.btn-primary {
  border-color: transparent;
  background: var(--accent);
  color: var(--accent-ink);
  box-shadow: 0 10px 24px -10px rgba(14, 165, 233, 0.75);
}

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

.btn-primary .icon-skip,
.btn-primary[data-mode="skip"] .icon-run {
  display: none;
}

.btn-primary[data-mode="skip"] .icon-skip {
  display: block;
}

.btn-primary[data-mode="skip"] {
  background: var(--surface-raised);
  border-color: var(--accent);
  color: var(--accent-bright);
  box-shadow: none;
}

select {
  width: 100%;
  min-width: 0;
  min-height: 44px;
  padding: 0 36px 0 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background:
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 12 8'%3E%3Cpath d='M1 1.5l5 5 5-5' fill='none' stroke='%2394a3b8' stroke-width='1.8' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E")
      no-repeat right 13px center / 12px 8px,
    var(--surface-raised);
  color: var(--text);
  font: 500 0.95rem/1.2 var(--font);
  appearance: none;
  cursor: pointer;
  transition: border-color var(--speed) var(--ease);
}

select:hover {
  border-color: #475569;
}

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

.segmented {
  display: inline-flex;
  align-items: center;
  gap: 3px;
  padding: 3px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}

.segmented-fill {
  display: flex;
}

.segmented-fill .segment {
  flex: 1;
}

.segmented-label {
  padding: 0 8px 0 9px;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 600;
}

.segment {
  position: relative;
  display: block;
}

.segment input {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  margin: 0;
  opacity: 0;
  cursor: pointer;
}

.segment span {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 40px;
  padding: 0 14px;
  /* Concentric with the segmented frame: its radius minus its 3px padding. */
  border-radius: calc(var(--radius) - 3px);
  color: var(--muted);
  font-weight: 600;
  font-size: 0.92rem;
  white-space: nowrap;
  transition:
    background-color var(--speed) var(--ease),
    color var(--speed) var(--ease),
    box-shadow var(--speed) var(--ease);
}

.segment:hover span {
  color: var(--text);
}

.segment input:checked + span {
  background: var(--accent-soft);
  color: var(--text);
  box-shadow: inset 0 0 0 1px rgba(56, 189, 248, 0.55);
}

.segment input:focus-visible + span {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

/* Page layout. On phones the stage and sidebar dissolve into one column so the
   board and its main actions come first; wider screens get two columns. */

.layout {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 12px;
  width: 100%;
  max-width: 1440px;
  margin: 0 auto;
  padding: 12px 16px 20px;
}

.stage,
.sidebar {
  display: contents;
}

.board-frame { order: 1; }
.actions { order: 2; }
.toolbar { order: 3; }
.status { order: 4; }
.stats-block { order: 5; }
.settings { order: 6; }
.legend { order: 7; }
.guarantees { order: 8; }
.guide { order: 9; }
.about { order: 10; }

.toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 14px;
}

.hint {
  color: var(--muted);
  font-size: 0.85rem;
}

.hint-coarse {
  display: none;
}

@media (pointer: coarse) {
  .hint-fine {
    display: none;
  }

  .hint-coarse {
    display: block;
  }
}

/* Phones: the status line already says what to do, so the board and its actions keep the first screen. */
@media (max-width: 599px) {
  .hint-fine,
  .hint-coarse {
    display: none;
  }
}

.board-frame {
  height: var(--board-height);
  padding: 8px;
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  background: var(--board-gap);
  box-shadow: var(--shadow), inset 0 0 0 1px rgba(148, 163, 184, 0.04);
}

.board-area {
  position: relative;
  width: 100%;
  height: 100%;
}

.board-area canvas {
  position: absolute;
  inset: 0;
  margin: auto;
  border-radius: 4px;
  touch-action: none;
  user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
  cursor: crosshair;
}

.board-area canvas:focus {
  outline: none;
}

.board-area canvas:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 16px;
  margin: 0;
  padding: 0 2px;
  list-style: none;
  color: var(--muted);
  font-size: 0.85rem;
}

.legend li {
  display: inline-flex;
  align-items: center;
  gap: 7px;
}

.swatch {
  width: 15px;
  height: 15px;
  flex: none;
  border-radius: 4px;
}

.swatch-start { background: var(--cell-start); }
.swatch-end { background: var(--cell-end); }
.swatch-empty { background: var(--cell-empty); box-shadow: inset 0 0 0 1px var(--border); }
.swatch-wall { background: var(--cell-wall); }
.swatch-frontier { background: var(--cell-frontier); }
.swatch-visited { background: var(--cell-visited); }

.swatch-weight {
  background:
    radial-gradient(circle at 50% 58%, var(--cell-weight-icon) 0 3px, transparent 3.5px),
    var(--cell-weight);
}

.swatch-path {
  background:
    linear-gradient(var(--cell-path), var(--cell-path)) center / 100% 5px no-repeat,
    var(--cell-path-fill);
}

/* Sidebar blocks */

/* Both buttons share a row when their labels fit, and stack otherwise. */
.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.actions .btn {
  flex: 2 1 auto;
  min-height: 48px;
  font-size: 1rem;
}

.actions .btn-primary {
  flex-grow: 3;
}

.status {
  min-height: 3.4em;
  padding: 10px 14px;
  border: 1px solid var(--border-soft);
  border-left: 3px solid var(--muted);
  border-radius: var(--radius);
  background: var(--surface);
  font-size: 0.92rem;
  transition: border-color var(--speed) var(--ease);
}

.status[data-tone="busy"] { border-left-color: var(--accent); }
.status[data-tone="success"] { border-left-color: var(--good); }
.status[data-tone="failure"] { border-left-color: var(--bad); }

.stats {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
  margin: 0;
}

.stat {
  min-width: 0;
  padding: 8px 9px;
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  background: var(--surface);
}

.stat dt {
  overflow: hidden;
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-overflow: ellipsis;
  text-transform: uppercase;
  white-space: nowrap;
}

.stat dd {
  margin: 1px 0 0;
  overflow: hidden;
  font-size: 1.12rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.card {
  padding: 14px 16px;
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
}

.card-title {
  margin-bottom: 10px;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

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

.settings .card-title {
  margin-bottom: 0;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
}

.field-label {
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 600;
}

.field-row {
  display: flex;
  gap: 8px;
}

.field-row select {
  flex: 1;
}

.guarantees table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
}

.guarantees th,
.guarantees td {
  padding: 7px 6px;
  border-bottom: 1px solid var(--border-soft);
  text-align: left;
  vertical-align: middle;
}

.guarantees tbody tr:last-child > * {
  border-bottom: 0;
}

.guarantees thead th {
  padding-top: 0;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 600;
}

.guarantees tbody th {
  font-weight: 600;
  transition: color var(--speed) var(--ease), box-shadow var(--speed) var(--ease);
}

.guarantees tbody tr {
  transition: background-color var(--speed) var(--ease);
}

.guarantees tbody tr[aria-current="true"] {
  background: rgba(14, 165, 233, 0.1);
}

.guarantees tbody tr[aria-current="true"] th {
  color: var(--accent-bright);
  box-shadow: inset 3px 0 0 var(--accent);
}

.pill {
  display: inline-block;
  padding: 2px 9px;
  border-radius: 999px;
  font-size: 0.76rem;
  font-weight: 700;
  white-space: nowrap;
}

.pill[data-tone="good"] { background: rgba(74, 222, 128, 0.14); color: var(--good); }
.pill[data-tone="warn"] { background: rgba(251, 191, 36, 0.14); color: var(--warn); }
.pill[data-tone="bad"] { background: rgba(251, 113, 133, 0.14); color: var(--bad); }
.pill[data-tone="neutral"] { background: rgba(148, 163, 184, 0.14); color: var(--muted); }

.disclosure {
  padding: 0 16px;
}

.disclosure summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 48px;
  font-weight: 650;
  cursor: pointer;
  list-style: none;
}

.disclosure summary::-webkit-details-marker {
  display: none;
}

.disclosure summary::after {
  content: "";
  width: 9px;
  height: 9px;
  margin-right: 4px;
  border-right: 2px solid var(--muted);
  border-bottom: 2px solid var(--muted);
  transform: rotate(45deg) translateY(-3px);
  transition: transform var(--speed) var(--ease);
}

.disclosure[open] summary::after {
  transform: rotate(225deg) translateY(-3px);
}

.disclosure[open] {
  padding-bottom: 14px;
}

.guide-list {
  display: grid;
  gap: 6px;
  margin: 0 0 14px;
  padding-left: 18px;
  color: var(--text);
  font-size: 0.9rem;
}

.keys,
.about-list {
  display: grid;
  gap: 8px;
  margin: 0;
  font-size: 0.9rem;
}

.keys > div {
  display: grid;
  grid-template-columns: minmax(96px, auto) 1fr;
  align-items: baseline;
  gap: 10px;
}

.keys dt {
  color: var(--muted);
  white-space: nowrap;
}

.keys dd,
.about-list dd {
  margin: 0;
}

.about-list dt {
  font-weight: 650;
}

.about-list dd {
  color: var(--muted);
}

/* Narrow phones: icon-only header button and no logo. */

@media (max-width: 440px) {
  .btn-collapse {
    padding: 0;
  }

  .btn-collapse .btn-text {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip-path: inset(50%);
    white-space: nowrap;
  }
}

@media (max-width: 359px) {
  .logo {
    display: none;
  }

  .segment span {
    padding: 0 10px;
  }
}

/* Two columns: desktops, tablets in landscape and phones turned sideways. */

@media (min-width: 900px), (min-width: 600px) and (orientation: landscape) {
  :root {
    --board-height: clamp(220px, calc(var(--viewport-height) - 188px), 900px);
  }

  .layout {
    display: grid;
    grid-template-columns: minmax(0, 1fr) clamp(280px, 32vw, 380px);
    align-items: start;
    gap: 20px;
    padding: 16px 24px 20px;
  }

  .stage,
  .sidebar {
    display: flex;
    flex-direction: column;
    gap: 12px;
    min-width: 0;
  }

  .stage > *,
  .sidebar > * {
    order: 0;
  }

  .stats {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 1100px) {
  .stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

/* Keep the board in view while a long sidebar scrolls, when the screen is tall enough for it. */
@media (min-width: 900px) and (min-height: 600px) {
  .stage {
    position: sticky;
    top: 12px;
  }
}

@media (min-width: 900px) {
  .app-header {
    padding: 12px 24px;
  }
}

/* Phones turned sideways: drop the hint and fit the board under the header. */
@media (max-height: 500px) and (orientation: landscape) {
  :root {
    --board-height: max(200px, calc(var(--viewport-height) - 156px));
  }

  .app-header {
    padding-block: 6px;
  }

  .hint-fine,
  .hint-coarse {
    display: none;
  }
}

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