Rules for the dvd piece:

1) dvd can be brought on the board by pawn promotion on any file except A and H
2) dvd moves diagonally, but can never occupy the corner squares.
3) DVD by default changes color after the turn of the color it currently is.
4) if no action is taken on DVD, it automatically moves along its course after the player completes their move, but before their turn is complete.
5) when DVD reaches a square on the side of the board, if no player acts on it, it bounces in the mirror diagonal direction
6) when reaching the side, the matching color player may move it one square along the side, except into the corners. Horizontal moves do not capture. Moving the DVD horizontally prevents it from changing color that turn (allowing it to be captured by the opponent). Moving the square affects the diagonal direction: e.g. if DVD is on a5, moving it to a6 causes it to move next towards b7. Moving it to a4 causes it to move towards b3. DVD is otherwise not under player control while it is not on the sides.
7) when meeting another piece diagonally, DVD takes the piece if it is the opposing color, or is blocked along its trajectory if it is the same color. DVD switches colors and continues its path, e.g. taking the piece that blocked it the previous turn, unless it has moved.

Optionally:

• DVD can not cause check or checkmate, and the king can be used as a bumper
• DVD can be spawned by a bishop capturing another bishop, if the previous move of the captured bishop is parallel to the direction of motion taken by the capturing bishop. "the bishop bang" spawns DVD with the color and direction of the capturing bishop on the first open space in its natural trajectory.