Battle of LITS is an abstract board game for 2 players. Players take turn placing tetrominoes (blocks of 4 squares, like Tetris pieces) onto the grid, following the rules of the puzzle LITS, as they secure their own symbols and cover the opponent's symbols. When there is no more piece that can be played, the player with more symbols still uncovered wins.

Start of the game

The board is 10x10 by size. Players can agree to play a predetermined pattern of symbols, or choose a random selection. With random selection, each player will have 30 symbols. (All but one of the patterns also have 30 symbols per player.) One player plays with X, the other O; the X player starts.

Player's turn

In a player's turn, a player must play a piece. Pieces occupy four squares, and are of four different shapes: L, I, T, and S. A piece must be played to follow the following rules:

• A piece must be played adjacent to a previously played piece (except, obviously, for the first piece played).
• There can be no 2x2 square completely covered by pieces.
• Two identical pieces may not be adjacent.

Otherwise, a player is free to play any piece in any position their wish, including rotating and reflecting the piece. The piece may cover any number of symbols of either player; the symbols only affect the scoring, not the legal plays.

There are only five pieces of each shape, and this pool of pieces is shared between both players. If a shape is exhausted, neither player can play more of that shape.

After playing a piece, the turn passes to the opponent.

The first turn and the pie rule

After the first turn, the second player has the option of switching sides. This switches the symbols of the players, and the second player takes the played move as theirs instead and letting the opponent to go again, effectively making the second player to be the first player. This "pie rule" option only exists in the first turn.

End of the game

If either player can no longer play any piece, the game ends. The player with more of their symbols that are still uncovered wins the game. In case of a tie, the player that played the last piece wins.