How to Defeat Each Boss
When beating boss one, make sure to have the red pistol equipped. While being the cheapest item in the game, you’ll use it for a ton of levels. Buy it as soon as you can. As soon as you start the boss fight, spam the shoot button. When he tries to attack you, just move to his other side (it’s pretty easy to dodge as he shoots bullets slowly into the air at first). You should be able to kill him before he progresses to shooting bullets everywhere in the sky.
Boss two is the easiest boss to beat in the game. As he is one shot by almost every gun in the game, you can shoot him right away to win. The fight doesn’t actually start until you drop down. However, you can jump right before you drop to jump in front of him. Shoot him with your red pistol once to end the battle. Repeat this to farm coins.
Boss three is also easy to beat. Choose the rocket launcher (the orange one) and dodge around the bullets to get as much damage as possible off (to dodge you just jump from platform to platform. Once you reach the top drop off and repeat). You should be able to kill him easily. WARNING: You will need to defeat him or get him to low HP before he reaches the stage of mass rockets. He starts off by shooting one bullet, but over time he goes to triple bullets, and then finally mass rockets (rockets are spammed and you’re dead if you get caught in it).
Boss four is probably the hardest boss out of them all. Choose the rocket launcher (again). You need to build a pattern up so you don’t die. Use the platforms to dodge the bullets. Once you reach the top, I recommend going to the other side (once he shoots the drills it’ll be hard to keep dodging from one side). Repeat this, and you should win the boss fight easily.
Boss five is the last boss. He starts by shooting blades at you from the ground. Dodge those, and he’ll shoot bullets at you. The bullets move up and down and track you. To beat this boss I would run up to the boss. After I got really close to him, I’d back up pretty far away (near the platform farthest away from the boss. Repeat this process (while shooting the boss the whole time).