This is an interesting spin on portal games, also the graphics are cool, although retro.
Overall, good game.
I'm gonna be honest, when we could only control one portal - it was somehow harder, then when you could control both. Also, I had a very short confusion about how I can control the player, when I realised, that I can't, I'll have to solve everything with the portals.
Other than that, I think most of the puzzles were quite good, not too hard, but you have to think / experiment a bit.