Hadron

Introduction
Hadron is a two player game played on a square board, initially empty. White and Blue take turns adding one checker of their own color, starting with White.

Placement Rule
You may place a checker in isolation, not adjacent to anything. Otherwise, the placement must form the same number of horizontal or vertical adjacencies with friendly and enemy checkers: one and one, or two and two.

Object of the Game
Passing is not allowed. If you have a placement available, you must make one. If you do not have a placement available on your turn, you lose.