help me
hey guys, i just bought a 2015 macbook pro and I'm not much of a gamer but i expected since this computer had Intel Iris 1536 i figured why not. So i purchased the game "Besiege" on steam and it's really fun only the graphics aren't crystal clear like they are in youtube videos and pictures of the game. And another problem is the computer heats up very fast while playing, therefore i can't play it long anyway. I figured their should be a high performance setting in system preferences, but their isn't. I also tried looking up automatic graphic switching but it seems the computer doesn't allow that option anyway. So I'm lost and don't know what to do next... Help!
MacBook Pro with Retina display, OS X Yosemite (10.10)