Mouse Goes Off Screen Dual Monitor Mac

Mac OSX Yosemite 10.10. Playing fullscreen on dual monitor. Game on right, browser on left. In game, if I mouse over to the far left quickly, the mouse will go out of the game and come back in. Doesn't seem like a big problem at first, but when you're spamming right click, it makes a ton of new folders on my other screen. Also, if it's towards the bottom, then it'll think the mouse is near the dock and give control to the secondary monitor in game so i can't use my keyboard or left click. I compared it to windowed and borderless mode and you can clearly see the mouse going off the screen and back to the game.

Whhyyyy [zombie-brand-mindblown]