Not sure what I messed up on here, but both the IK and the center bones have the Limit Rotation constraint, with the same values. Now, I want the mesh to only rotate on the x-axis. But right now, it's more like free-for-all. Before I've made a minecraft rig and it works all right. What do I need to fix this?
EDIT: I figured out, that it may be because the shoulder is frozen in on eposition and won't rotate when you use the IK. Not sure what's up. I tried following this tutorial: Blender tutorial