Inertia is a game of unification in the sense of Claude Soucie's Lines of Action. The first player to unite all of his pieces on the board into a single group wins. To start, white places one piece anywhere on the 8x8 square board. Players then alternate placing pieces on the board, with the first piece being adjacent to the opponent's most recently placed piece and the second piece being adjacent to no pieces, either orthogonally or diagonally. Once a player can't place a second piece, the placement phase ends and the next player starts the movement phase. On a turn, a player moves one piece akin to a queen in chess, with movement ending after passing through any number of empty spaces or by landing on an opponent's piece and capturing it. If this move increases the total number of groups on the board — with a group being a single stone or a series of straight- or diagonally-connected like-colored stones — then the move is illegal. Gameplay continues until one player unites all of his pieces into a single group; if he simultaneously creates single groups for both players, then the game is a draw. Instead of using a chess board, Inertia can be played on a hexhex board with pieces moving like hex rooks.