body {
  margin: 0;
  overflow: hidden;
  background-color: #000;
  font-family: Arial, sans-serif;
}

canvas {
  display: block;
  background-color: #111;
}

/* Start, Game Over, and Options Overlays */
#startOverlay, #gameOverOverlay, #optionsOverlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: rgba(0, 0, 0, 0.8);
  z-index: 20;
}

#startOverlay, #optionsOverlay {
  flex-direction: column;
}

#gameOverOverlay {
  flex-direction: column;
  display: none;
}

#startOverlay button, #gameOverOverlay button, #optionsOverlay button {
  padding: 15px 30px;
  font-size: 24px;
  cursor: pointer;
  border: none;
  border-radius: 10px;
  background-color: #222;
  color: #fff;
  transition: transform 0.2s, box-shadow 0.2s;
  margin: 10px;
}

#startOverlay button:hover, #gameOverOverlay button:hover, #optionsOverlay button:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #fff;
}

.game-over-text {
  color: #fff;
  font-size: 36px;
  margin-bottom: 20px;
}

/* Options overlay styling */
.options-container {
  background: #222;
  padding: 20px;
  border-radius: 10px;
  text-align: center;
  color: #fff;
}

/* Upgrade overlay styling */
#upgradeOverlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: none;
  align-items: center;
  justify-content: center;
  background-color: rgba(0, 0, 0, 0.8);
  z-index: 10;
}

#optionsOverlay {
  display: none;
}


.upgrade-container {
  display: flex;
  gap: 20px;
}

/* Upgrade card design with rounded corners and hover glow */
.upgrade-card {
  background: #222;
  padding: 20px;
  margin: 10px;
  color: #fff;
  text-align: center;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  border-radius: 10px;
  min-width: 150px;
}

/* Upgrade card borders matching their glow colour */
.upgrade-card.rarity-common { border: 2px solid #aaa; }
.upgrade-card.rarity-uncommon { border: 2px solid #66ccff; }
.upgrade-card.rarity-rare { border: 2px solid #00f; }
.upgrade-card.rarity-epic { border: 2px solid #f0f; }
.upgrade-card.rarity-legendary { border: 2px solid #ff0; }

/* Rarity-specific hover glow */
.upgrade-card.rarity-common:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #aaa;
}
.upgrade-card.rarity-uncommon:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #66ccff;
}
.upgrade-card.rarity-rare:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #00f;
}
.upgrade-card.rarity-epic:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #f0f;
}
.upgrade-card.rarity-legendary:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #ff0;
}