Where

To play, launch the hosted version at http://not-there.herokuapp.com/ (it will take a while to load since it packs some heavy tunes - have patience)

Collaborative mode works for two players at a time only (and multiplayer restart button won't work properly, you'll have to refresh upon dying)

Play solo mode if you don't know what you're doing.

Click to add portals, A-D / LEFT-RIGHT to move, W / UP key to sprint, right click to add markers.

Enjoy

Github: https://github.com/paulvarache/not-there