* { box-sizing: border-box; }
html, body {
  margin: 0;
  padding: 0;
  background: #000;
  overflow: hidden;
  width: 600px;
  height: 600px;
  font-family: 'Courier New', monospace;
  color: #00ffff;
  touch-action: none;
  -webkit-user-select: none;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}
#game {
  display: block;
  width: 600px;
  height: 600px;
}
#hud {
  position: absolute;
  inset: 0;
  width: 600px;
  height: 600px;
  pointer-events: none;
  user-select: none;
}
#score {
  position: absolute;
  top: 16px;
  left: 16px;
  font-size: 22px;
  text-shadow: 0 0 8px #00ffff;
}
#wave {
  position: absolute;
  top: 16px;
  right: 16px;
  font-size: 22px;
  text-shadow: 0 0 8px #00ffff;
}
#hp-bar {
  position: absolute;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  width: 400px;
  height: 16px;
  border: 2px solid #00ffff;
  box-shadow: 0 0 8px #00ffff;
}
#hp-fill {
  width: 100%;
  height: 100%;
  background: #33ff66;
  transition: width 120ms linear, background 200ms linear;
}
#indicators {
  position: absolute;
  left: 0;
  top: 0;
  width: 600px;
  height: 600px;
  pointer-events: none;
}
#crosshair {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 32px;
  height: 32px;
  pointer-events: none;
  display: none;
}
#crosshair::before,
#crosshair::after {
  content: '';
  position: absolute;
  background: #66ff66;
  box-shadow: 0 0 6px #66ff66;
}
#crosshair::before {
  left: 50%;
  top: 4px;
  bottom: 4px;
  width: 2px;
  transform: translateX(-50%);
}
#crosshair::after {
  top: 50%;
  left: 4px;
  right: 4px;
  height: 2px;
  transform: translateY(-50%);
}
@keyframes fire-pulse {
  0%   { transform: translate(-50%, -50%) scale(1); filter: none; }
  30%  { transform: translate(-50%, -50%) scale(1.5); filter: brightness(2); }
  100% { transform: translate(-50%, -50%) scale(1); filter: none; }
}
#crosshair.fire-pulse {
  animation: fire-pulse 140ms ease-out;
}
#menu, #game-over {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 32px;
  pointer-events: auto;
  text-align: center;
}
#menu h1 {
  font-size: 40px;
  margin: 0;
  letter-spacing: 4px;
  text-shadow: 0 0 12px #00ffff;
}
#menu p, #game-over p {
  font-size: 18px;
  margin: 0;
}
.focusable {
  min-width: 200px;
  min-height: 88px;
  border: 3px solid #00ffff;
  background: transparent;
  color: #00ffff;
  font-family: inherit;
  font-size: 24px;
  letter-spacing: 4px;
  cursor: pointer;
  outline: none;
  box-shadow: 0 0 12px #00ffff;
}
.focusable:focus,
.focusable:hover {
  background: rgba(0, 255, 255, 0.15);
  box-shadow: 0 0 20px #00ffff, inset 0 0 12px #00ffff;
}
#game-over h1 {
  font-size: 36px;
  color: #ff3366;
  text-shadow: 0 0 12px #ff3366;
  margin: 0;
}
#flash {
  position: absolute;
  inset: 0;
  background: #ff0033;
  opacity: 0;
  transition: opacity 100ms linear;
  mix-blend-mode: screen;
  pointer-events: none;
}