OK I beat every level so this is what you do.
On the first level shoot all the big brown ships that drop stuff when you kill them and when one of them drops a chaser missile. Get it. The chaser missile weapon upgrade looks like a missile pointing toward the top rite corner. Once you get that go to the bottom left corner and STAY THERE hold down the fire button and the weapon will fire like 3 missiles and they will follow the enemy’s. Then do the the rest of the game with that weapon and the weapon will eventually get to level five where it is white and most powerful the only thing you have to worry about the rest of the game is dodging. Oh yea i almost forgot choose the driver that is slow and has a high shield. Also DON'T use the EMP on the bosses it does not work and you will waste it. Use it when you are surrounded. That’s all.

Still waiting for a better one!XD