:root {
  --tile-bg: #d6e9ff;
  --tile-bg-alt: #c6def7;
  --tile-selected: #8fbff5;
  --tile-peer: #e8f1fb;
  --tile-same: #b3d4f7;
  --given: #0a1f3d;
  --player: #1f6feb;
  --error: #d6336c;
  --error-bg: #ffd6e0;
  --grid-line: #2c4a73;
  --grid-thick: #16335c;
  --bg: #f4f8ff;
  --panel: #ffffff;
  --text: #1b2733;
  --muted: #6b7a8c;
  --accent: #1f6feb;
  --accent-dark: #0b4fc4;
  --shadow: 0 2px 8px rgba(20, 50, 100, 0.08);
}

:root[data-theme="dark"] {
  --tile-bg: #1a3a5c;
  --tile-bg-alt: #164080;
  --tile-selected: #2563eb;
  --tile-peer: #0f2744;
  --tile-same: #1e40af;
  --given: #e0e9ff;
  --player: #60a5fa;
  --error: #f472b6;
  --error-bg: #7c2d42;
  --grid-line: #1e3a5f;
  --grid-thick: #0a1f3d;
  --bg: #0a1f3d;
  --panel: #1a3a5c;
  --text: #e0e9ff;
  --muted: #94a3b8;
  --accent: #60a5fa;
  --accent-dark: #3b82f6;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  min-height: 100%;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  background: var(--panel);
  box-shadow: var(--shadow);
}
.topbar h1 { margin: 0; font-size: 1.4rem; color: var(--accent-dark); }
.user-area { display: flex; align-items: center; gap: 10px; }
.user-info { font-size: 0.9rem; color: var(--muted); }

.layout {
  display: grid;
  grid-template-columns: 240px 1fr 260px;
  gap: 20px;
  padding: 20px;
  max-width: 1200px;
  margin: 0 auto;
}

.left-panel, .right-panel {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.settings, .status, .leaderboard, .numpad-wrap, .actions {
  background: var(--panel);
  border-radius: 10px;
  padding: 14px;
  box-shadow: var(--shadow);
}
.settings { display: flex; flex-direction: column; gap: 10px; }

.field { display: flex; flex-direction: column; gap: 4px; font-size: 0.9rem; color: var(--muted); }
.field select {
  padding: 8px;
  border-radius: 6px;
  border: 1px solid #cdd6e0;
  background: white;
  font-size: 1rem;
}
.field.toggle { flex-direction: row; align-items: center; gap: 8px; color: var(--text); }

.btn {
  border: 1px solid #cdd6e0;
  background: white;
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 0.95rem;
  cursor: pointer;
  color: #1b2733;
  font-weight: 500;
  transition: background 0.15s, transform 0.05s;
}
.btn:hover { background: #f0f6ff; border-color: #8fbff5; }
.btn:active { transform: translateY(1px); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: white; font-weight: 600; }
.btn.primary:hover { background: var(--accent-dark); }
.btn.ghost { background: transparent; color: #1b2733; }
.btn.ghost:hover { background: rgba(31, 111, 235, 0.1); }
.btn.toggle-btn.active { background: var(--accent); color: white; border-color: var(--accent); font-weight: 600; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

:root[data-theme="dark"] .btn {
  border-color: #2c5a8c;
  background: #0f2744;
  color: #e0e9ff;
}
:root[data-theme="dark"] .btn:hover { background: #1a3a5c; border-color: #3b7fab; }
:root[data-theme="dark"] .btn.ghost { background: transparent; color: #e0e9ff; border-color: #2c5a8c; }
:root[data-theme="dark"] .btn.ghost:hover { background: rgba(96, 165, 250, 0.15); border-color: #3b7fab; }

.status { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.status-item { display: flex; flex-direction: column; }
.status-item span { font-size: 0.75rem; color: var(--muted); text-transform: uppercase; }
.status-item strong { font-size: 1.1rem; }

.board-wrap {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  position: relative;
}

.board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  width: min(540px, 90vw);
  aspect-ratio: 1 / 1;
  background: var(--grid-thick);
  border: 3px solid var(--grid-thick);
  border-radius: 6px;
  gap: 1px;
  user-select: none;
  touch-action: manipulation;
}

.cell {
  background: var(--tile-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(1rem, 4vw, 1.8rem);
  font-weight: 600;
  color: var(--player);
  cursor: pointer;
  position: relative;
  transition: background 0.15s;
}
.cell.given { color: var(--given); font-weight: 700; }
.cell.error { color: var(--error); background: var(--error-bg); }
.cell.peer { background: var(--tile-peer); }
.cell.same-num { background: var(--tile-same); }
.cell.selected { background: var(--tile-selected); border: 3px solid var(--accent); }

/* Thicker borders for 3x3 boxes */
.cell[data-col="2"], .cell[data-col="5"] { box-shadow: inset -2px 0 0 var(--grid-thick); }
.cell[data-row="2"], .cell[data-row="5"] { box-shadow: inset 0 -2px 0 var(--grid-thick); }
.cell[data-col="2"][data-row="2"], .cell[data-col="2"][data-row="5"],
.cell[data-col="5"][data-row="2"], .cell[data-col="5"][data-row="5"] {
  box-shadow: inset -2px 0 0 var(--grid-thick), inset 0 -2px 0 var(--grid-thick);
}

.notes {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  font-size: clamp(0.5rem, 1.4vw, 0.7rem);
  color: var(--muted);
  font-weight: 500;
}
.notes span {
  display: flex;
  align-items: center;
  justify-content: center;
}

.numpad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}
.num {
  background: white;
  border: 1px solid #cdd6e0;
  border-radius: 8px;
  padding: 14px 0;
  font-size: 1.3rem;
  font-weight: 600;
  cursor: pointer;
  color: var(--accent-dark);
  transition: background 0.15s;
}
.num:hover { background: #f0f6ff; }
.num.active { background: var(--accent); color: white; border-color: var(--accent); }
.num.exhausted { opacity: 0.35; }

.actions { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }

.leaderboard h3 { margin: 0 0 8px; font-size: 0.95rem; color: var(--muted); text-transform: uppercase; }
.leaderboard ol { margin: 0; padding-left: 20px; font-size: 0.9rem; }
.leaderboard li { padding: 2px 0; }
.score-note { margin: 8px 0 0; font-size: 0.75rem; color: var(--muted); font-style: italic; }

.message {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  background: white;
  color: #1b2733;
  border: 2px solid var(--accent);
  padding: 18px 24px;
  border-radius: 12px;
  box-shadow: var(--shadow);
  font-size: 1.2rem;
  font-weight: 700;
  pointer-events: none;
  z-index: 10;
}

:root[data-theme="dark"] .message {
  background: #0f2744;
  color: #e0e9ff;
  border-color: #3b7fab;
}

.footer {
  padding: 16px 20px;
  text-align: center;
  background: var(--panel);
  margin-top: 20px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}
.donate { display: inline-flex; gap: 10px; align-items: center; flex-wrap: wrap; justify-content: center; }
.donate-btn {
  text-decoration: none;
  background: #fff7d6;
  border-color: #f0d97a;
  color: #6b5300;
  font-weight: 600;
}
.donate-btn:hover { background: #fff0a8; }
.legal-links { display: flex; gap: 16px; justify-content: center; font-size: 0.9rem; }
.legal-links a { color: var(--text); text-decoration: none; }
.legal-links a:hover { color: var(--accent); }
.build-stamp { font-size: 0.75rem; color: var(--muted); margin-top: 12px; font-family: monospace; opacity: 0.6; }

/* Stats modal */
.stats-modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 20px;
}
.stats-content {
  background: var(--panel);
  color: var(--text);
  border-radius: 12px;
  padding: 28px;
  max-width: 480px;
  width: 100%;
  max-height: 80vh;
  overflow-y: auto;
  position: relative;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
  border: 1px solid var(--border, #cdd6e0);
}
.stats-close {
  position: absolute;
  top: 12px;
  right: 12px;
  background: transparent;
  border: none;
  font-size: 28px;
  cursor: pointer;
  color: var(--muted);
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
}
.stats-close:hover { background: rgba(0, 0, 0, 0.05); color: var(--text); }
.stats-content h2 { margin: 0 0 20px; color: var(--accent-dark); font-size: 1.4rem; }
.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 20px;
}
.stats-card {
  background: var(--bg);
  padding: 14px;
  border-radius: 8px;
  border: 1px solid var(--border, #cdd6e0);
}
.stats-card .label { font-size: 0.75rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.05em; }
.stats-card .value { font-size: 1.4rem; font-weight: 700; color: var(--text); margin-top: 4px; }
.stats-section { margin-bottom: 16px; }
.stats-section h3 { font-size: 0.95rem; color: var(--muted); text-transform: uppercase; margin: 0 0 8px; letter-spacing: 0.05em; }
.stats-list { list-style: none; padding: 0; margin: 0; }
.stats-list li {
  display: flex;
  justify-content: space-between;
  padding: 6px 0;
  border-bottom: 1px solid var(--border, #e5e9ef);
  font-size: 0.9rem;
}
.stats-list li:last-child { border-bottom: none; }
.stats-empty { color: var(--muted); text-align: center; padding: 20px; font-style: italic; }

:root[data-theme="dark"] .stats-content { border-color: #2c5a8c; }
:root[data-theme="dark"] .stats-card { border-color: #2c5a8c; background: #0a1f3d; }
:root[data-theme="dark"] .stats-list li { border-color: #2c5a8c; }
:root[data-theme="dark"] .stats-close:hover { background: rgba(255, 255, 255, 0.1); }

/* Flash gradient animation for completed row/col/box */
@keyframes flashGradient {
  0% { background: #1f6feb; }
  100% { background: var(--tile-bg); }
}
.cell.flash {
  animation: flashGradient 1s ease-out;
}

:root[data-theme="dark"] .cell.flash {
  animation: flashGradientDark 1s ease-out;
}
@keyframes flashGradientDark {
  0% { background: #93c5fd; }
  100% { background: var(--tile-bg); }
}

/* Dissolve animation for game completion */
@keyframes dissolveOut {
  0% { transform: scale(1) rotate(0); opacity: 1; }
  100% { transform: scale(0.2) rotate(20deg); opacity: 0; }
}
.cell.dissolve {
  animation: dissolveOut 0.6s forwards;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
    padding: 12px;
    gap: 12px;
  }
  .left-panel, .right-panel { order: 2; }
  .board-wrap { order: 1; }
  .status { grid-template-columns: repeat(4, 1fr); }
  .numpad { grid-template-columns: repeat(9, 1fr); }
  .num { padding: 10px 0; font-size: 1.1rem; }
  .actions { grid-template-columns: repeat(4, 1fr); }
}