Cool little game. I'm impressed you made the engine yourself, I have no clue how any of that works so that's pretty cool in my books. Took my brain a bit to realize how the stage was set up. At first I thought it was just all flat, but I was able to eventually see the 3D ness of it. I will point out it's fairly easy since you can just spam shoot and pretty much destroy everything before you get to it. Maybe having limited ammo or certain environment blocks that are indestructible would help.
Good work!