Verified answer

This video will explain it better than I can write it.

http://www.youtube.com/watch?v=piXCWW77RVc

I had a ton of exciting enjoying Portal, the flash version. And there grew to become into yet another sport, i won't be able to remember the call of it, yet you used those power balls and you pull them back like a slingshot to interrupt those vehicles that strengthen on your base... It used a good number of rather sturdy physics and collision harm and stuff like that. I performed it for like 2-3 days and that i won't be able to remember the freaking call of it. edit - lol, that guy stated portal too... could be a physically powerful sport.