locking a axel

Hi again!
I created a very small prototype of a gameplay. Its puzzlelike there u move a ball with moving the whole level, moving the ball from A to B.
This game is going to be 2d, and I create this in blender cuz its powerful gravity-engine.

the question I want help with is how to lock the ball from direction Y, I want the ball only goes with X and Z-axels, left&right, up&down.

I post the blenderfile of my work, not much but its a early prototype.
http://hem.passagen.se/luffaren_bill_gates/gravityroller.rar

//yeahman

try a constraint actuator , assign it to anything except Z… Z is broken

Now I dont understand what constraint actuator is, help me, explain how to lock Y…

I checked the stuff about constraint, still not get it…
//yeahman:confused:

here is how i would do it.
add an empty and a cube. make the cube an actor with rigibody enabled. then add a rigidbody constraint with generic selected onto the cube with the linminy, angminy, angminx, angminz buttons clicked. make the toObject the empty. That should prevent any movement in the y direction, however it will also neutralize any rotation. to get a rotation object to do this just delete all the vertices in the cube and make it a ghost, but keep all the other settings the same. Now add a sphere and make it rigidbody. Add a rigidbody constraint to the sphere and have the toObject as the cube. Make it a ball joint. that should git her done