:root {
  --bg: #07131f;
  --bg-soft: #102033;
  --panel: rgba(11, 28, 46, 0.9);
  --panel-border: rgba(164, 202, 255, 0.18);
  --text: #edf5ff;
  --muted: #96a9c0;
  --accent: #6ce0ff;
  --accent-2: #8ceca6;
  --warm: #ffc857;
  --danger: #ff7a59;
  --shadow: 0 20px 60px rgba(0, 0, 0, 0.25);
  --radius-xl: 26px;
  --radius-lg: 18px;
  --radius-md: 14px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: "Trebuchet MS", "Segoe UI", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(108,224,255,0.14), transparent 26%),
    radial-gradient(circle at top right, rgba(255,122,89,0.12), transparent 24%),
    linear-gradient(180deg, #08121c 0%, #102033 55%, #07131f 100%);
}

a { color: inherit; text-decoration: none; }
button, input { font: inherit; }
button { cursor: pointer; }

/* Prevent text selection and long-press highlight on touch devices to avoid the browser selection overlay.
   This improves controls on mobile where holding a button or double‑tapping should not select its text. */
button,
.controls button,
.grid-buttons button,
.board button {
  user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  touch-action: manipulation;
}

.page {
  width: min(100% - 20px, 1080px);
  margin: 0 auto;
  padding: 18px 0 32px;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 14px;
  margin-bottom: 20px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
}

.brand__mark {
  width: 46px;
  height: 46px;
  display: grid;
  place-items: center;
  border-radius: 16px;
  font-weight: 800;
  color: #07131f;
  background: linear-gradient(135deg, var(--accent), var(--danger));
}

.brand__text {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.brand__text strong {
  font-size: 1.15rem;
  font-family: "Georgia", serif;
}

.brand__text small { color: var(--muted); }

.topbar__back {
  padding: 11px 16px;
  border-radius: 999px;
  border: 1px solid var(--panel-border);
  background: rgba(255,255,255,0.04);
  color: var(--text);
}

.hero,
.layout__board,
.layout__side,
.status-bar,
.stats,
.panel {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  box-shadow: var(--shadow);
}

.hero {
  border-radius: var(--radius-xl);
  padding: 24px;
  margin-bottom: 18px;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.18em;
  font-size: 0.76rem;
}

.hero h1 {
  margin: 0 0 10px;
  font-size: clamp(2rem, 5vw, 3.6rem);
  line-height: 1.02;
  font-family: "Georgia", serif;
}

.hero p:last-child,
.hint,
.muted,
.status-bar { color: var(--muted); }

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(240px, 320px);
  gap: 18px;
}

.layout__board,
.layout__side,
.panel {
  border-radius: var(--radius-xl);
  padding: 18px;
}

.layout__board {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px;
  border-radius: var(--radius-lg);
  padding: 14px;
}

.stat {
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.06);
  border-radius: var(--radius-md);
  padding: 12px;
}

.stat strong {
  display: block;
  font-size: 1.2rem;
  color: var(--text);
}

.stat span {
  font-size: 0.88rem;
  color: var(--muted);
}

.status-bar {
  border-radius: var(--radius-lg);
  padding: 14px 16px;
}

.actions,
.controls,
.grid-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.button,
.controls button,
.grid-buttons button,
.board button {
  min-height: 48px;
  padding: 11px 16px;
  border-radius: 14px;
  border: 1px solid var(--panel-border);
  background: rgba(255,255,255,0.04);
  color: var(--text);
}

.button--primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #07131f;
  border: none;
  font-weight: 700;
}

.canvas-wrap {
  display: flex;
  justify-content: center;
}

canvas {
  width: min(100%, 420px);
  height: auto;
  border-radius: 18px;
  background: #08121c;
  border: 1px solid rgba(255,255,255,0.08);
  touch-action: none;
}

.board {
  display: grid;
  gap: 10px;
}

.board--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.board--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.board--8 { grid-template-columns: repeat(8, minmax(0, 1fr)); gap: 6px; }

.cell {
  display: grid;
  place-items: center;
  min-height: 64px;
  aspect-ratio: 1 / 1;
  border-radius: 16px;
  border: 1px solid var(--panel-border);
  background: rgba(255,255,255,0.05);
  color: var(--text);
}

.cell--big {
  min-height: 82px;
  font-size: clamp(1.2rem, 3vw, 1.7rem);
  font-weight: 800;
}

.pad {
  display: grid;
  gap: 10px;
}

.pad--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.pad--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.note-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.note {
  padding: 12px 14px;
  border-radius: 14px;
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.05);
  color: var(--muted);
}

@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }
}

@media (max-width: 640px) {
  .page { width: min(100% - 14px, 1080px); }
  .topbar { flex-direction: column; align-items: stretch; }
  .topbar__back { text-align: center; }
  .hero, .layout__board, .layout__side, .panel { padding: 16px; }
}