I was assuming top down game, which is where set angle toward, pathfinding, 8-direction are useful. If it's a side-scrolling left-to-right mario platformer I don't think you need to make use of set angle toward player, you could give the boss platform behaviour and have it simulate movements left to right towards the player object and if the boss X > set animation facing right, if x < set animation facing left that kind of thing. Instead of platform behaviour you could also just move toward the player at the given angle. You could do this in 3 events, move boss forward a number of pixels (at given angle), if boss.x > player.x set angle 180, if boss.x < player.x set angle 0 in its basic form. I mention platform behaviour on the boss because if you are wanting to simulate it jumping and chasing you then this behaviour will be useful.