Players take turns filling out a 3 by 3 board with O's and X's. The first player to make a line wins.

message State {
  // Required field to indicate the player who should be making the next move
  // Values = 0 or 1
  int32 player_turn_idx = 1;

  /*
  Array of size 9 initialized to -1, representing an empty 3 by 3 board.
  The values of board can be -1, 0, or 1. 
  Placing a piece in index x will set the value of board[x] to the player's index.
  Array is row major order: index 0 is top left, index 2 is top right, index 6 is 
  bottom left, and index 8 is bottom right.
  */
  repeated int32 board = 2;
}
