Every move must end on the same color square it started on. That means your knights can never move, your pawns can only double-step or capture, and your king and rooks step diagonally or an even number of squares.
Chameleonis one of Nerf Chess's secret handicaps. In Nerf mode you choose one of two nerfs before the first move, in secret, and carry it for the whole game.
The board quietly enforces it: any move it forbids is simply never offered, so you cannot break it by accident. Your opponent never sees which nerf you took until the game ends, so every move you make is also a clue they are trying to read.
“Blend in. Never break pattern.”
Affects your kings, pawns, knights, and rooks.