This version of 3D chess uses planar moves and advancement squares.

The board has been promoted by a dimension, so must the moves. Instead of advancing in straight lines, pieces advance in flat planes.

This requires an expanded definition of direction, and the loss of the classical concept of trajectory.

No variation of the rules that insist on straight line moves can achieve play in 3D that feels like chess. The rules cannot be invented, they must be discovered.

This first version to be released to the public (0.6) meets the standards of Minimal Viable Product (MVP). Much remains to be done, but it does provide enough tools for players to confirm if a move is legal.