Destroy enemies with your melee weapon, throwing shuriken and bombs as you traverse a tower. Try not to lose all of your health, you will have two more chances to continue from the floor on which you died. You can only start the game from the top floor of the tower until you defeat the bosses on the lower floors.
Use Arrow keys to move, Z to attack, X to throw shuriken and C to bomb. New weapons will be unlocked as you progress.