It's quite difficult, but it's really really fun :D
It's not as hard as it looks. It seems as if for some of the challenges you merely have to take advantage of the golden second. In other words, its not possible to succeed unless you complete a certain minimum number of actions in that interval.
100% completed after I think 45 mins at least.
Pretty difficult, it requires concentration, patience, a lot of nerves too. But I like to suffer with those games in order to train myself (I'm a complete slowpoke).
And even I managed to get them all. Word of advice (I know it pisses off people and I like it) : Get good scrubs w00t !
The hardest games for me :Tiling, Sweeping (omg), rotating (urgh !) and finally Avoiding (NUKE EVERYTHING !)
Shooting was the easiest !
Some of the criteria required for the medals are simply beyond the current capability of my mouse...
A fun, difficult game.