Well, I lost a few hours to making my collision work. It all happened because I wanted to drive my GameObjects exclusively on my own, and not depend on the PhysX engine.

The relevant Unity physics documentation page that explains how to make this work is a little more obscure than you’d expect at first, but if you’re making a Unity game where 1) You’re not using the PhysX engine and 2) You want to detect collisions, then here’s what you need to do:

• Give rigidbodies to all your colliders.
• On those rigidbodies, set isKinematic to true.
• On the collider, set isTrigger to True.
• Detect collisions in the trigger functions, OnTriggerXXX(), not OnCollisionXXX().

That’s it! I’m happy I figured this out during a Ludum Dare, and not on a more important project, but either way I’m glad I know what to do next time.