City Square Off challenges two players to each build a well-designed city that doesn't spill over the boundary lines that govern play. Each player starts with a 9x9 playing area that has a different cityscape starter tile in the middle of it and a set of 21 city tiles. Game play takes place simultaneously, with one player turning over a shape card – each showing a Tetris-style arrangement of squares that matches one of the city tiles – and both players then adding the matching tile to their cities. Tiles must be placed with at least one edge adjacent to the starter tile or another tile in play. If a player would be forced to go outside the 9x9 city grid, that player loses; if both players would lose on the same turn, then the player with the largest contiguous group of open spaces is dubbed master city planner and wins the game.