Shoot two Elec Balls

Get two Elec ammo pieces (you can use one, but two is recommended), then take Danny’s Slingshot and hold Shoot to fire two Elec Balls while only using one ammo piece. -From: efd581

Defeating the big robot

When fighting the first Boss (the big robot), go over to the side but do not fall off. Shoot his arms and lasers as quickly as possible on each side. You can save time and health. If you get hit by lasers, do not worry because you will only lose a small amount of health.