:root {
  --bg-gradient-start: #1a1a2e;
  --bg-gradient-end: #16213e;
  --cell-default: #5d6d7e;
  --cell-red: #e33434;
  --cell-blue: #3c8be0;
  --accent-yellow: #ffd700;
  --text-color: #f0f0f0;
}

body {
  background: linear-gradient(135deg, var(--bg-gradient-start), var(--bg-gradient-end));
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  overflow: hidden; /* Prevent scrollbars if board fits */
}

/* Top Left Image Styling */
.solved-example {
  position: absolute;
  top: 20px;
  left: 20px;
  width: 150px;
  height: auto;
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0,0,0,0.3);
  border: 2px solid rgba(255, 255, 255, 0.1);
  opacity: 0.9;
  transition: transform 0.3s ease;
}

.solved-example:hover {
  transform: scale(1.05);
  opacity: 1;
}

/* Main Container */
.game-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  z-index: 10; /* Ensure board is above background */
}

h1 {
  color: var(--text-color);
  margin-bottom: 25px;
  font-weight: 300;
  letter-spacing: 1px;
  text-shadow: 0 2px 4px rgba(0,0,0,0.5);
}

#board {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px; /* Slightly increased gap */
  padding: 20px;
  background: rgba(255, 255, 255, 0.03); /* Subtle glass effect behind board */
  border-radius: 20px;
  box-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
}

/* Row Styling */
.row {
  display: flex;
  justify-content: center;
  gap: 16px; /* Slightly increased gap between cells */
}

/* Cell Styling */
.cell {
  width: 65px;
  height: 65px;
  border-radius: 50%;
  border: none;
  background-color: var(--cell-default);
  cursor: default;
  box-shadow: inset 0 -4px 6px rgba(0,0,0,0.2), 
              0 4px 8px rgba(0,0,0,0.3); /* Inner and outer shadow for depth */
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

/* Color Variants */
.red {
  background-color: var(--cell-red);
  box-shadow: inset 0 -4px 6px rgba(0,0,0,0.3), 
              0 4px 8px rgba(227, 52, 52, 0.4);
}

.blue {
  background-color: var(--cell-blue);
  box-shadow: inset 0 -4px 6px rgba(0,0,0,0.3), 
              0 4px 8px rgba(60, 139, 224, 0.4);
}

/* Interactive Center Cells */
.center {
  cursor: pointer;
  outline: none;
  border: 3px solid var(--accent-yellow);
  box-shadow: 0 0 15px rgba(255, 215, 0, 0.4), 
              inset 0 -4px 6px rgba(0,0,0,0.3), 
              0 4px 8px rgba(0,0,0,0.3);
}

.center:hover {
  transform: scale(1.1);
  box-shadow: 0 0 20px rgba(255, 215, 0, 0.6), 
              inset 0 -4px 6px rgba(0,0,0,0.3), 
              0 6px 12px rgba(0,0,0,0.4);
}

.center:active {
  transform: scale(0.95);
  box-shadow: 0 0 10px rgba(255, 215, 0, 0.3), 
              inset 0 -2px 4px rgba(0,0,0,0.3), 
              0 2px 4px rgba(0,0,0,0.2);
}

/* Empty cells (value 0) can have a slightly different look if desired */
.cell:not(.red):not(.blue) {
  background-color: #6c7a89;
}