Fantastic! I love the mechanic. I'd love to see this as a full post-jam game, although I'm not sure how extensible the mechanic is (it'd need something more to make it work). This is really well polished game with great art and music. Best I've seen this jam, it's a shame you haven't gotten many ratings yet!
As for critical feedback - my main complaint is that esc quits the entire game and resets; several times I tried to leave the level and ended up quitting the game. Also, it was sometimes tricky to get enough speed from the portal; maybe presets would help?
Overall, incredible game, easy perfect rating.