I can do it either cross-eyed or wall-eyed, and can flick between them over a couple of seconds. I do find it easiest when a bit tired, or after a long night programming.

I do practice moving my eyes in different directions, though. I think it's an important skill babies have but we lose.

Study the chameleon, and it shall show the way

On a separate note - I can't do this game at all. I guess tech issues with my machine mean it just loads a dark green screen and nothing else.