Portal

Portal: The Flash Version includes over 40 challenging, portals thinking levels, which features almost every feature the real game does, in 2d - energy balls, cubes, turrets and even the famous crusher from the trailer. The game also includes a console to mess around with after finishing the game, or just being frustrated by thinking with portals (Commands are posted in our forums)

portal.wecreatestuff.com

Controls:
Left mouse button - launch a portal.
A W D - movement
Q - launch a blue portal.
E - launch a yellow portal.
R - Close both portals.
F - pick up an object.
~ - open up console (enable through the options)
O - quick quality adjust.
Esc/P - pause game.