A few details about co-op play. Co-op is basically the same as the main campaign. There are about 10 additional puzzles unique to co-op that require two players to cooperate. All the other puzzles are mostly the same, although some are slightly changed and some are removed because they are not suitable for two players... Most notably, the puzzles removed include: keypad puzzle at the end of chapter one, the big elevator puzzle in chapter one and the entire chapter three which is really a single-player puzzle and the other player would get bored. In co-op, both players need to stand at the telephone booth to save the checkpoint. There are no hats to collect. Instead. players get to pick a hat to wear at the start of the game. All these changes mean that co-op is easier to play than single player mode. However there are a couple of puzzles that are a little bit harder because both players need to sync their movements (for example: jumping the loose floors in chapter 4). Additionally, a combination of one very skilled and one average skilled player also works well, because most puzzles can be solved mainly by skilled player while the other one just follows and moves/jumps at right moment. This means that both players can think about possible solutions, and once they figure it out, the more skilled one can execute it.