There are a few bugs with the portal collisions ( maybe due to the mix of 2D/3D ? ), but I think it's a good game for the On/Off theme !
PS : Maybe too much dialogs before level, I think it breaks the game's rhythm.
By the way, if you're interested, I've also explored the dimension shifting concept ( black/white ) in my game, which is also a platformer ( but in speedrun mode ). Feel free to give it a try...