:root {
  --bg-color: #f3f6f8;
  --card-bg: #ffffff;
  --text-primary: #191919;
  --text-secondary: #5e5e5e;
  --border-color: #e0e4e8;
  --cell-bg: #f8fafc;
  --cell-border: #d0d7de;
  --cell-hover: #eef2f6;
  --cell-visited: #e0f2fe;

  --accent-blue: #0a66c2;
  --accent-hover: #004182;
  --path-stroke: #0284c7;
  --path-gradient-start: #0284c7;
  --path-gradient-end: #0ea5e9;
  --checkpoint-bg: #ffffff;
  --checkpoint-border: #0a66c2;
  --checkpoint-text: #0a66c2;
  --checkpoint-visited-bg: #0a66c2;
  --checkpoint-visited-text: #ffffff;
  --checkpoint-next-glow: 0 0 14px rgba(10, 102, 194, 0.45);

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 12px 28px rgba(0, 0, 0, 0.15);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-full: 9999px;

  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

[data-theme="dark"] {
  --bg-color: #0f172a;
  --card-bg: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --border-color: #334155;
  --cell-bg: #1e293b;
  --cell-border: #334155;
  --cell-hover: #293548;
  --cell-visited: #0c4a6e;

  --accent-blue: #38bdf8;
  --accent-hover: #0284c7;
  --path-stroke: #38bdf8;
  --path-gradient-start: #38bdf8;
  --path-gradient-end: #818cf8;
  --checkpoint-bg: #1e293b;
  --checkpoint-border: #38bdf8;
  --checkpoint-text: #38bdf8;
  --checkpoint-visited-bg: #38bdf8;
  --checkpoint-visited-text: #0f172a;
  --checkpoint-next-glow: 0 0 16px rgba(56, 189, 248, 0.55);

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 14px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 12px 28px rgba(0, 0, 0, 0.5);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-color);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  padding: 12px 16px 24px;
  transition: background-color 0.25s ease, color 0.25s ease;
  overflow-x: hidden;
}

.app-container {
  width: 100%;
  max-width: 520px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

/* Header */
.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 4px 0;
}

.logo-area {
  display: flex;
  align-items: center;
  gap: 8px;
}

.logo-badge {
  background: linear-gradient(135deg, #0a66c2 0%, #0091ff 100%);
  color: white;
  font-weight: 900;
  font-size: 1.15rem;
  letter-spacing: 0.5px;
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  box-shadow: 0 2px 6px rgba(10, 102, 194, 0.3);
}

.game-title {
  font-size: 1.35rem;
  font-weight: 800;
  letter-spacing: -0.5px;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.icon-btn {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 38px;
  height: 38px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.15s ease;
  box-shadow: var(--shadow-sm);
}

.icon-btn:hover {
  color: var(--accent-blue);
  border-color: var(--accent-blue);
  transform: translateY(-1px);
}

/* Difficulty Selector Bar */
.difficulty-bar {
  display: flex;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 4px;
  gap: 4px;
  box-shadow: var(--shadow-sm);
}

.difficulty-btn {
  flex: 1;
  padding: 8px 6px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 0.85rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.18s ease;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.difficulty-btn span.grid-size {
  font-size: 0.7rem;
  opacity: 0.75;
  font-weight: 500;
}

.difficulty-btn.active {
  background: var(--accent-blue);
  color: #ffffff;
  box-shadow: 0 2px 8px rgba(10, 102, 194, 0.35);
}

.difficulty-btn.active span.grid-size {
  opacity: 0.9;
}

/* Game Info / Status Bar */
.status-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 10px 14px;
  box-shadow: var(--shadow-sm);
}

.status-stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.stat-label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
  font-weight: 600;
}

.stat-value {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
  font-variant-numeric: tabular-nums;
}

.next-target-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: var(--radius-full);
  background: var(--accent-blue);
  color: white;
  font-size: 0.8rem;
  font-weight: 800;
}

/* Board Wrapper */
.board-container {
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1;
  background: var(--card-bg);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 12px;
  box-shadow: var(--shadow-md);
  display: flex;
  align-items: center;
  justify-content: center;
  touch-action: none; /* Prevents scroll during drawing */
}

.board-grid {
  display: grid;
  width: 100%;
  height: 100%;
  gap: 6px;
  position: relative;
  z-index: 2;
}

.cell {
  position: relative;
  background-color: var(--cell-bg);
  border: 1.5px solid var(--cell-border);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background-color 0.15s ease, border-color 0.15s ease, transform 0.1s ease;
}

.cell:hover {
  background-color: var(--cell-hover);
}

.cell.visited {
  background-color: var(--cell-visited);
  border-color: rgba(14, 165, 233, 0.4);
}

.cell.head {
  border-color: var(--accent-blue);
  box-shadow: inset 0 0 0 2px var(--accent-blue);
}

.cell.hint-highlight {
  animation: pulse-hint 1s infinite alternate;
}

@keyframes pulse-hint {
  from {
    background-color: rgba(245, 158, 11, 0.2);
    border-color: #f59e0b;
    box-shadow: 0 0 8px rgba(245, 158, 11, 0.5);
  }
  to {
    background-color: rgba(245, 158, 11, 0.4);
    border-color: #d97706;
    box-shadow: 0 0 16px rgba(245, 158, 11, 0.7);
  }
}

/* Checkpoint Disc */
.checkpoint-disc {
  width: 38px;
  height: 38px;
  border-radius: var(--radius-full);
  background-color: var(--checkpoint-bg);
  border: 2.5px solid var(--checkpoint-border);
  color: var(--checkpoint-text);
  font-size: 1.1rem;
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 5;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.12);
  transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
  pointer-events: none;
}

.grid-size-7 .checkpoint-disc,
.grid-size-8 .checkpoint-disc {
  width: 30px;
  height: 30px;
  font-size: 0.95rem;
  border-width: 2px;
}

.checkpoint-disc.active-target {
  box-shadow: var(--checkpoint-next-glow);
  transform: scale(1.08);
}

.checkpoint-disc.passed {
  background-color: var(--checkpoint-visited-bg);
  color: var(--checkpoint-visited-text);
  border-color: var(--checkpoint-visited-bg);
  box-shadow: 0 2px 8px rgba(10, 102, 194, 0.3);
}

/* SVG Path Overlay */
.path-svg {
  position: absolute;
  top: 12px;
  left: 12px;
  width: calc(100% - 24px);
  height: calc(100% - 24px);
  pointer-events: none;
  z-index: 3;
}

.path-line {
  fill: none;
  stroke: url(#path-gradient);
  stroke-linecap: round;
  stroke-linejoin: round;
  filter: drop-shadow(0 2px 5px rgba(2, 132, 199, 0.35));
  transition: stroke-dashoffset 0.15s ease;
}

/* Active Head Glowing Dot */
.head-glow-dot {
  position: absolute;
  width: 14px;
  height: 14px;
  border-radius: var(--radius-full);
  background: #ffffff;
  border: 3px solid var(--accent-blue);
  box-shadow: 0 0 10px rgba(10, 102, 194, 0.8), 0 0 20px rgba(10, 102, 194, 0.5);
  transform: translate(-50%, -50%);
  pointer-events: none;
  z-index: 6;
  animation: head-pulse 1.4s infinite ease-in-out;
}

@keyframes head-pulse {
  0%, 100% {
    transform: translate(-50%, -50%) scale(1);
    box-shadow: 0 0 8px rgba(10, 102, 194, 0.7);
  }
  50% {
    transform: translate(-50%, -50%) scale(1.25);
    box-shadow: 0 0 16px rgba(10, 102, 194, 0.9);
  }
}

/* Bottom Controls */
.controls-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}

.control-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 10px 4px;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.8rem;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: all 0.15s ease;
}

.control-btn svg {
  width: 18px;
  height: 18px;
  fill: currentColor;
}

.control-btn:hover:not(:disabled) {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  transform: translateY(-1px);
}

.control-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.control-btn.btn-primary {
  background: var(--accent-blue);
  color: white;
  border-color: var(--accent-blue);
}

.control-btn.btn-primary:hover:not(:disabled) {
  background: var(--accent-hover);
  color: white;
}

/* Secondary toolbar (Game mode toggle: Daily, Level Pack, Practice) */
.mode-tabs {
  display: flex;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 4px;
  gap: 4px;
}

.mode-tab {
  flex: 1;
  padding: 8px 10px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.15s ease;
  text-align: center;
}

.mode-tab.active {
  background: var(--cell-hover);
  color: var(--accent-blue);
}

/* Modal Dialog Styles */
dialog.game-modal {
  margin: auto;
  border: none;
  background: transparent;
  padding: 0;
  max-width: 440px;
  width: 90%;
  outline: none;
}

dialog.game-modal::backdrop {
  background: rgba(0, 0, 0, 0.55);
  backdrop-filter: blur(4px);
}

.modal-content {
  background: var(--card-bg);
  color: var(--text-primary);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 16px;
  text-align: center;
}

.modal-title {
  font-size: 1.4rem;
  font-weight: 800;
  letter-spacing: -0.3px;
}

.win-badge-icon {
  font-size: 3rem;
  line-height: 1;
}

.win-stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
  background: var(--cell-bg);
  padding: 12px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
}

.win-stat-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.win-stat-label {
  font-size: 0.72rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  font-weight: 600;
}

.win-stat-val {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent-blue);
}

.modal-buttons {
  display: flex;
  gap: 10px;
}

.modal-btn {
  flex: 1;
  padding: 12px;
  border-radius: var(--radius-md);
  font-weight: 700;
  font-size: 0.95rem;
  cursor: pointer;
  border: none;
  transition: all 0.15s ease;
}

.modal-btn.primary {
  background: var(--accent-blue);
  color: white;
}

.modal-btn.primary:hover {
  background: var(--accent-hover);
}

.modal-btn.secondary {
  background: var(--cell-bg);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.modal-btn.secondary:hover {
  background: var(--cell-hover);
}

.rules-list {
  text-align: left;
  display: flex;
  flex-direction: column;
  gap: 10px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.45;
}

.rules-list li {
  margin-left: 20px;
}

.rules-list strong {
  color: var(--text-primary);
}

.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(50px);
  background: #1e293b;
  color: white;
  padding: 10px 18px;
  border-radius: var(--radius-full);
  font-size: 0.85rem;
  font-weight: 600;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.25);
  pointer-events: none;
  opacity: 0;
  transition: transform 0.25s cubic-bezier(0.175, 0.885, 0.32, 1.275), opacity 0.25s ease;
  z-index: 10000;
}

.toast.show {
  transform: translateX(-50%) translateY(0);
  opacity: 1;
}

/* Keyboard hint banner */
.keyboard-hint {
  font-size: 0.72rem;
  color: var(--text-secondary);
  text-align: center;
  opacity: 0.8;
}