It's an interesting concept, but I had multiple issues with the game.
First off, the first level is way too difficult without a tutorial, and I had to spend many minutes figuring out the mechanics via trial and error. This includes learning that the two background colours are in fact both part of the background and not separate platform layers (e.g. platforms you can place portals on, grey background you can move around in, green is completely "solid").
Placing portals were finicky. Sometimes it didn't place portals where I wnted them, sometimes not at all. Maybe an indicator where the portal would be placed based on mouse positon would be useful, especially since it seems to be grid based?
I liked that going though a portal changed your gravity based on the angle you exit it.