Graphics freeze after playing for a while.

Put the summary of the bug you're having here

What I expected to happen was...:
I can play endlessly and be able to see what I'm doing.

What actually happened was...:
After playing for an extended period of time, my game freezes for a second then unfreezes, though the graphics remain frozen.

Steps to Reproduce:
I have no idea. It just started happening and just happens randomly.