The levels were originally made for the portal gun in gmod, which was plenty glitchy. Now it's works for portal. runs about an hour long, have fun!

http://www.garrysmod.org/downloads/?a=viewid=23137

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it's very pretty, but most of the puzzles (so far, i got to the part with the ball sitting there) are quite literally impossible. they all seem to want combine energy balls, but there are none... and the first room? Is it some kind of joke?