Addicting...
My high scores:
Daily 2nd 527 Insane, Weekly 21st 527 Insane
Daily 4th 582 Hard
Daily 13th 404 Extreme
Daily 13th 606 Easy
I honestly find Insane to be the easiest mode... O.o
Also, I'm just 90% Accuracy and "Pwong Pwner" on extreme away from getting all the achievements...