First things First , do not attempt the perfect boss runs until you have maxxed the Photon Launcher. Also if you get hit by the boss , simply die and continue and try again. The checkpoints are just before each boss in the game
Method for the Boss Fight
Easiest Boss of the game. Start off By shooting all the little turrets and avoiding their shots. Now stand directly in the middle of the boss and shoot upwards. Once the boss dissapears move off to the left as the middle gets hit. Just keep firing and the Boss should be dead before he can hit you with any other moves.