I am thinking of taking econ 3M03 game theory this summer term. The only econ I've taken is 1b03 and 1bb3.

So is it a good idea? what is the general difficulty of the course?

....umm shouldn't you at least do 1 second year course before you even thing about 3rd year. Anyways from what I hear that course is heavily micro based and its not by any means a bird course. Im not completely sure though as im not in 3rd year. I think you may need to take at least a second yr micro class to take 3M03, but again im not sure