Cool puzzles, I could definitely see the portal influence. The perspective made it hard to control at times, but great job making a 3D game in such a short period of time. The movement and mechanics are very polished.
Personally I would change the white/grey grid texture since it looks like a default texture placeholder. It sort of makes the levels look like a greybox placeholder. Other than that, I actually really like the simplicity. Having the shadow guy mirror you and switch places is a really cool concept, nice job!