Click on the screen to fire a mine in that direction.
If the number at the bottom of the screen matches the target it will be destroyed.
It's explosion will show you how many points you score.
Click the arrows to cycle through the possible numbers for the level.
If your health reaches zero the game is over. Hitting targets and completing levels
give you health. Letting ships leave the screen decreases your health.
Click "Game Over" to start again.