[ODE] 2D dynamics in ODE

[Luke Palmer]

My friends and I are making an "educational" Incredible Machine clone,
and I'm seriously considering using ODE as the physics engine.  It's a
2D game, and ODE is a 3D engine.

So I'm wondering whether ODE will be stable if I give all points a z=0.
That is, can I be assured that no z component will ever arise?

If I can't, is there a way to tell ODE to maintain this constraint for
me?  Any other ideas?

Thanks,
Luke