Nice game 4/5, it has great game play all you got to do is make it more difficult, maybe a bit harder than the 3'rd chapter. Suggestions on making it harder: Make enemies turn around sooner, it's too easy when they just hit the wall and turn around, maybe make them run past you a bit but than follow you, and making them jump would make them more difficult. Make the things the drip acid drip the acid in bigger droplets, they're too easy to avoid. Make those flying guys shoot, I found those to be the toughest enemy to beat by the way. I think you should add checkpoints in the levels instead of giving the player a lot of hp, but that's just me. And for the weapons maybe instead of having to buy them you have to find them, or unlock them after beating a level. Because I think I got the ray gun on the 5'th level, making the game easy. So basically, you got a good game, just improve level design. 4/5!
Pro Tip for the hard badge: It's gonna take you a while and you need everything maxed. Stay on one side so you can concentrate on just that side it makes it easier. Good luck and 5/5 for the game!
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