I clicked "save and quit" and it took really long to save. In fact, I don't think it saved at all. Java said it crashed and I closed the program, then started minecraft up again. Now all of my worlds have invisible floors and strange, black shapes where trees and rocks should be! Even when I start a new world, this happens. It is completely unplayable! I have screenshots...
if this deos not work reinstall minecraft
if it still deos not work then i cannot do anything