Okay, so this game was pretty neat!
Having the 2 player characters to swap between in order to complete platforming puzzles was really interesting and added a lot. However, this mechanic had some bugs, namely that I could trap myself in walls by teleporting the player up to the other character. This was really annoying at times. You should do a check if the space is taken up by a collider and try to put the character on the other side.
There's no sound, which was a bit of a bummer, although time constraints get in the way and I understand.
Graphically the game is a bit dull, but the player sprites are quite good. I'd ease up on the repetitive tiles though.
Having multiple enemy types (the gray one could fly, right?) was cool, but the gray ghost got bugged for me and it was easy to cheese by just getting him stuck against a surface while flying past it and he remains this way until made to switch directions away from the wall. You should adjust your collisions to allow sliding across, which would negate this.
The theme wasn't really implemented as it was more of a teleport than a rewind, I mean, they weren't rewinding to a previous position or anything, just moving to each other's new positions.
The 3rd ability could have said what it did, as it was confusing at first.
Cool idea though!