Rock Portal Scissors Achievement
Rock Portal Scissors20
Win 3 co-op games of rock-paper-scissors in a row
This can be gained in Course 1 – Team Building Test Chamber 4 and can be gained in either split-screen or over XBL.
First off you can only unlock the achievement if you initiate the gesture! You'll unlock this gesture when you start chamber 4. Now just face one another and choose the Rock, Paper & Scissors gesture on the right. You need to win 3 in a row and its all down to luck.
If your guy cheers and jumps around then its a win, if he puts his head in his hands its a loss and if both of them shake their heads is a draw which does not count as a loss or win. See below for a little trick on how to get it faster.
The game seems to cheat you out a lot when you reach 2 wins and the 3rd is always a loss. As stated above you must initiate the gesture for it to unlock BUT its does not matter when! I noticed that when your partner did the gesture, you would get 2 wins in a row most of the time!
So have you partner initiate the gesture, let your guy get 2 wins, then you initiate the next one for the 3rd win in a row. You now have a higher chance on winning 3 in a row doing it this way instead of you constantly doing the gesture.