I haven't got past the first level, but that is the reasoning behind the first link. Short-term memory only lasts for so long and there is only so many things you can keep. Angry Birds is something you can play naturally with only your instincts. For a challenge you have to get three stars.

At its core, both The Impossible Game and Angry Birds are simple, but one is more successful to past to the next level. If you get one star on Angry By Birds, you can pass. On The Impossible game you have to have timing and be aware of what is coming up. I suspect this is the reason why the original Super Mario Bros. became so popular.