Standard Neutron Rules for All Variants:
 
Each player has a home-row filled with pawns of his color. There is also a neutral piece in the center of the board called the Neutron; neither player owns it. The object of the game is to move the Neutron to a square in your own home-row, or to force your opponent to move the Neutron to your home-row, or to stalemate the opponent so he can't complete part of his turn.
 
All pieces move in the same way, in a straight line in any direction, orthogonally or diagonally. A piece must move as far as it can in one direction; it continues until it is blocked by a wall or another piece. There is no capturing. Each turn consists of two parts: moving the Neutron and then moving a friendly Pawn. White goes first. In order to compensate for the advantage of going first, White doesn't move the Neutron on the very first turn.
 
Restricted Variants:
A player's pawns may not move onto his opponent's home-row.
 
Doubly-Restricted Variants:
A player's pawns may not move onto either his opponent's home-row, or his own home-row.
 
Neutron was originally invented by Robert A. Kraus in 1978. (See the original Zillions game for more information.) The new variants were made in 2001. The restricted versions are based on an idea of David Ploog.