[xxcdzzbc] 3D keyboard

When learning to touch type on a typical flat keyboard, one needs to learn the location of keys in a flat 2D area.  When learning to touch type on a Kinesis keyboard with its keys arranged in a bowl, one needs to learn the location of keys and directions to push in 3D space.

Hypothesize that the latter (despite more dimensions) is easier, because tactile things arranged in 3D space is more natural.

Kinesis is a concave bowl.  Consider the opposite, keys on a convex dome.

Or, from a given rest position, fingers may move in multiple directions in 3D to push different keys.  Inspired by woodwind instruments.