This is one of the best looking games I've played the Jam so far (100+ games) and the core concept is a lot of fun. If you wanted to take this further (and you definitely should) I would suggest some kind of system that stops players from just running through the level and straight to the portal. Maybe it only works when you've killed x number of enemies? But a fantastic and very good looking experience.
Also, please make the font a little bigger on your game page. It is very small and hard to read. Thanks