Click and hold to build up power, then release to shoot. If you run out of ammunition, visit the munitions master (all the way to the left) to reload. Purchase upgrades between levels.
Sink all the enemy ships to complete a level. The green bar next to a ship is its health meter. If your ship sinks or the castle is destroyed, its game over!
Right/Left or A/D = Move
Mouse = Aim & Shoot