my current preoccupation is a simply yet addicting game called "Daleks" based on the BBC show Doctor Who.
it is free online HERE
basically, you are on a board where you have to avoid the Daleks while tricking them into crashing into each other. you can also teleport to a random location on the board, and you have a sonic screwdriver that kills any Daleks on nearby squares.
it seems simply, but it is addicting.
Try it out.