You spawn with a rotating cannon at the bottom and a block at the top with 1. The number corresponds to the hitpoints required to remove the block. 1 bullet deals one damange per contact, but the total damage depends on the amount of times a bullet makes contact with a block. The number next to the cannon indicates the amount of bullets available to you. Each turn, the blocks descend downwards by one level, with a new layer of blocks spawning behind. Subsequent blocks spawn with higher required hitpoints, but you also gain more bullets accordingly. The game is lost when a block escapes the grey enclosure.