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

:root {
  --bg-deep: #0f1220;
  --bg-panel: #171b2e;
  --bg-panel-2: #1f2540;
  --text: #eef1ff;
  --text-muted: #9aa3c7;
  --accent: #7c6cff;
  --accent-glow: rgba(124, 108, 255, 0.35);
  --success: #4ecdc4;
  --border: rgba(255, 255, 255, 0.08);
  --cell-bg: #252b45;
  --cell-size: min(14vw, 56px);
  --radius: 14px;
  --font: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

html,
body {
  margin: 0;
  min-height: 100%;
  font-family: var(--font);
  background:
    radial-gradient(ellipse 80% 60% at 50% -10%, rgba(124, 108, 255, 0.22), transparent),
    radial-gradient(ellipse 60% 40% at 100% 100%, rgba(78, 205, 196, 0.12), transparent),
    var(--bg-deep);
  color: var(--text);
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

#app {
  min-height: 100dvh;
}

.screen {
  display: none;
  min-height: 100dvh;
  flex-direction: column;
}

.screen.active {
  display: flex;
}

/* Title */
#screen-title {
  align-items: center;
  justify-content: center;
  padding: 2rem;
}

.title-card {
  text-align: center;
  max-width: 420px;
}

.logo-mark {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-bottom: 1.25rem;
}

.logo-mark span {
  width: 10px;
  height: 42px;
  border-radius: 999px;
  background: linear-gradient(180deg, #ff6b6b, #4ecdc4, #a78bfa);
  animation: pulse 2.4s ease-in-out infinite;
}

.logo-mark span:nth-child(2) { animation-delay: 0.2s; }
.logo-mark span:nth-child(3) { animation-delay: 0.4s; }

@keyframes pulse {
  0%, 100% { transform: scaleY(1); opacity: 0.85; }
  50% { transform: scaleY(1.15); opacity: 1; }
}

.title-card h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(2.4rem, 8vw, 3.4rem);
  letter-spacing: 0.04em;
  background: linear-gradient(135deg, #fff 20%, #b8b0ff 80%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.tagline {
  margin: 0 0 2rem;
  color: var(--text-muted);
  font-size: 1.05rem;
}

.fine-print {
  margin: 1rem 0 0;
  font-size: 0.82rem;
  color: var(--text-muted);
}

/* Buttons */
.btn {
  border: none;
  border-radius: 999px;
  font: inherit;
  cursor: pointer;
  transition: transform 0.12s ease, box-shadow 0.12s ease, background 0.12s ease;
}

.btn:active {
  transform: scale(0.97);
}

.btn.primary {
  padding: 0.85rem 2.4rem;
  font-size: 1.05rem;
  font-weight: 600;
  color: #fff;
  background: linear-gradient(135deg, var(--accent), #5b4fd9);
  box-shadow: 0 8px 28px var(--accent-glow);
}

.btn.primary:hover {
  box-shadow: 0 10px 34px rgba(124, 108, 255, 0.5);
}

.btn.secondary {
  padding: 0.65rem 1.2rem;
  color: var(--text);
  background: var(--bg-panel-2);
  border: 1px solid var(--border);
}

.btn.ghost {
  width: 42px;
  height: 42px;
  color: var(--text);
  background: transparent;
  border: 1px solid var(--border);
  font-size: 1.1rem;
}

/* Top bar */
.top-bar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border);
  background: rgba(15, 18, 32, 0.85);
  backdrop-filter: blur(8px);
}

.top-bar h2 {
  margin: 0;
  font-size: 1.1rem;
  letter-spacing: 0.06em;
}

.spacer {
  flex: 1;
}

.level-info {
  flex: 1;
  text-align: center;
}

#level-label {
  display: block;
  font-size: 0.78rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.level-name {
  display: block;
  font-weight: 600;
}

/* Level select */
.level-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 0.85rem;
  padding: 1.25rem;
  flex: 1;
  align-content: start;
}

.level-btn {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.25rem;
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-panel);
  color: var(--text);
  text-align: left;
  cursor: pointer;
  transition: border-color 0.15s, transform 0.12s;
}

.level-btn:hover {
  border-color: rgba(124, 108, 255, 0.45);
  transform: translateY(-2px);
}

.level-btn.completed {
  border-color: rgba(78, 205, 196, 0.45);
}

.level-btn.completed .level-num::after {
  content: ' ✓';
  color: var(--success);
  font-size: 0.85rem;
}

.level-num {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--accent);
}

.level-title {
  font-weight: 600;
}

.level-size {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* Game board */
.game-area {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

#board-wrap {
  padding: 12px;
  border-radius: calc(var(--radius) + 4px);
  background: var(--bg-panel);
  border: 1px solid var(--border);
  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.35);
}

#board {
  display: grid;
  grid-template-columns: repeat(var(--cols), var(--cell-size));
  gap: 4px;
  touch-action: none;
  user-select: none;
}

.cell {
  width: var(--cell-size);
  height: var(--cell-size);
  border-radius: 10px;
  background: var(--cell-bg);
  position: relative;
  cursor: crosshair;
}

.cell.filled {
  background: color-mix(in srgb, var(--thread) 28%, var(--cell-bg));
  box-shadow: inset 0 0 0 2px color-mix(in srgb, var(--thread) 55%, transparent);
}

.cell.endpoint .dot {
  position: absolute;
  inset: 22%;
  border-radius: 50%;
  background: var(--thread);
  box-shadow: 0 0 12px color-mix(in srgb, var(--thread) 60%, transparent);
  pointer-events: none;
}

.cell.filled.endpoint .dot {
  inset: 18%;
}

.game-footer {
  display: flex;
  justify-content: center;
  gap: 0.75rem;
  padding: 1rem 1rem 1.4rem;
}

/* Win dialog */
#dialog-win {
  border: none;
  border-radius: var(--radius);
  padding: 0;
  background: var(--bg-panel);
  color: var(--text);
  max-width: 360px;
  width: calc(100% - 2rem);
  box-shadow: 0 24px 64px rgba(0, 0, 0, 0.5);
}

#dialog-win::backdrop {
  background: rgba(8, 10, 18, 0.72);
  backdrop-filter: blur(4px);
}

.dialog-body {
  padding: 1.75rem 1.5rem 1.5rem;
  text-align: center;
}

.win-badge {
  width: 56px;
  height: 56px;
  margin: 0 auto 1rem;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--bg-deep);
  background: linear-gradient(135deg, var(--success), #7ee8e0);
}

.dialog-body h2 {
  margin: 0 0 0.5rem;
}

.dialog-body p {
  margin: 0 0 1.25rem;
  color: var(--text-muted);
}

.dialog-actions {
  display: flex;
  gap: 0.65rem;
  justify-content: center;
}

@media (max-width: 480px) {
  :root {
    --cell-size: min(17vw, 52px);
  }

  .game-footer {
    flex-direction: column;
    align-items: stretch;
  }
}