Getting the movement physics to work at all was very tricky. The mass of the feet is increased significantly when the player is trying to stand upright with the legs to make them "stick" to the ground. This is determined by the orientation of the Joy-Cons and whether the feet are touching the ground. When the system thinks that the player should be standing upright, then it also adds upwards force to the head to pull the body up.

This worked well enough so that it's possible to make the character walk in an intended direction. For the demo video above, each room's footage was actually filmed in a single take. The system works!