How to make character move only in two direction?

Rather than character moving in all three axis, I want him to move only in two: up-down and right-left.

I do know how to do that with BodyPosition, but to spice things up, I wanna change the angle in which character can move. That means if he can move left-right, I want him to move bit forward-backward.

If you can't make sense of what I am saying, try to imagine coordinate system with X and Y axis. That will be the "bird view" of character moving. There, X axis would be character moving with normal BodyPosition.maxForce(0,0,500000). Now imagine a line that goes 30° relative to X axis. My question is, how do I make character move on that 30° line?

are you trying to make a 2d game?