I'm not extremely hot for platformers, so I might be biased. Having said that I'd actually want to start by praising the level design which, despite formulaic was very effective in presenting the concepts of the game early on without the need of a tutorial. Megaman much? Maybe. But it is fun at least in the beginning. The tutorial is ugly and messy but it does convey the idea well and it ends super soon. I did like the design for the robot, which, once again, maybe was not the most original ever but had enough going for it that I was actually frustrated for killing the poor thing (take this as my manly way o' saying the character was cute).
Now there was only one thing that really bothered me and it was the cheap gimmick of bringing people to the beginning of the stage every time they took damage. I know you were going for Nintendo Hard in here but it did feel cheap to have my progress fade away that easily. In fact, my sense of progression felt so hindered that i couldn't go farther then mid-level 2, because, by then, I had died so many times I just didn't care anymore. Sure you could argue i'm a quitter but the premise hinted that I'd barely have any reward for trying harder so I'd simply shrug and go play another game.
But I did say above that I'm not a platformer guy and I'm sure the old-school metroidviana crowd will be pleased with this piece because it doesn't treat you like an idiot as long as you don't read the instructions and proves you are a promising level designer with the right inspirations.
Keep up the good work and I hope you get through the Portal.