When I open a game the screen flickers very fast. It's only sometimes. I was just playing a game fine, then I decided to switch to a superflat to play with luck tables, now it won't stop. When on superflat it starts out with what seems to be rotating grass textures, then it gets worse and villages begin flashing around but they're not really there. Most of the time I can just walk through, others I'm obstructed by one of the several village layouts I am seeing. When on a standard world (even on LAN) it flashes all sorts of different layouts and blocks and biomes and let's just say I'm very glad I don't have epilepsy. I hope I've provided enough info to help, let me know if there's more I can give you.