Do you know Valve's Portal that's part of The Orange Box? There's an impressive 2-D Flash Game that's very similar to Portal (yet in no way related to Valve). It's one of the most sophisticated Flash Games we've seen so far - and thus also pretty large in filesize (about 7 MB). As Subject 15837 you have to find a way out of each stage using your Portal Gun. There are 40 levels to solve.