Game 10: Portal

A 2D online version of the original PC/XBOX360/PS3 game; Portal: The Flash Version includes over 40 levels, and has almost every feature the orinal game does, all in glorious 2D! If you're not familiar with the original game, Portal is an extremely frustrating and addictive puzzler, the basic idea being to use your portal gun to get to the exit on each level. Definately worth a look.

Left Mouse Button - launch a portal      R - close both portals
Arrow Keys - movement                       F - pick up an object
Q - launch a blue portal                       O - adjust graphics quality 
E - launch a yellow portal                     Esc/P - pause game