When your wand passes over a lighter, it ignites a spark which flares red and then turns white as it starts to burn down its fuse. If your hand hits the spark after the spark turns white, you lose a life. Eventually, the spark detonates a bomb.
The exploding bomb inflicts damage in several ways: it kills nearby hands (including perhaps your own!); it destroys nearby spikes, acid droplets, walls, and switches; it removes the bonus from nearby dots.
