cursor stuck in minecraft window

I just installed minecraft on OSX 10.10.3. When the MC window opens the cursor is stuck in that window - I can't get it out to resize the window (which opens up very small by default) or access any other application. This is totally impractical.

The only way I can access anything else on the computer is to quit MC completely. I'm using a trackpad, but I also tried plugging in a mouse and the problem is the same.