Yeahh, I couldn't perfect the AI of the green robots. When you get right in front of them, they charge back and attack you but it doesn't kill in one hit like the blue robots' bullets do. Because of this, I kind of just left the green robots there to give players the satisfaction of killing them, and designed the difficulty around the levels based on the blue robots.
I also agree with the slow death animation. I'm pretty inexperienced with animating, so I went with something simple (like the robots' helmet turning red then grey implying they power up). It sounded like a good idea to me in theory, but in practice it kind of takes away from the fast paced gameplay which I want. Having the robots disappear and there being a cloud of smoke did not occur to me, I LOVE that idea. I will be learning more about particles and effects in hopes of doing something like that in the future. Thanks for playing and for giving your feedback!