Based on Valve's Portal, Portal: The Flash Version brings it all up in 2d!
Portal: The Flash Version includes over 40 challenging, portals thinking levels, and everything's included, 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!

Game 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.

Put one portal in the roof and one portal on the floor beneath.
Fall through the portals to gain speed.
Move the roofportal to the ground next to the wall while you're falling through the air.