Ok think i've fixed the alt-F4 problem now, see if it still causes you problems.
He doesnt actually look for collissions, he follows a set of patterns and collides if you're in the way.
But you think it would be better if he avoided you?
I deliberately made one pattern come forward so that the player is given a reason to move forwards rather than sit at the back of the screen.
I was thinking of using a variation of the patterns in this demo for the lvl1 boss.