Pieces move one orthogonal space and capture by replacement.
The initial board set-up consists of a piece in its portal surrounded on all five sides by friendly pieces. The two 2x2 boards on the bottom right also form a regular 3D board. These two 3D boards are connected through the fourth dimension, such that each space in one 3D board is orthogonally adjacent to its counterpart in the other. The two 3D boards on the bottom thus form a 4D board. The two 3D boards on the top similarly form a 4D board.