Get ontop
Have 1 player go to where the plasma pistol is. (NOT the one on the roof thing, the other one) Have him jump on another players head. Then make them all keep tapping jump. Player 1 should jump off of the other players head in the air and jump up to the platform. Have player 1 face the street. Then take another player and have him go to where the brute sot ammo is. (NOT the one by the sniper!) You will see a small black peg you can jump on. Jump on that then jump on the little flap above the small window. Then jump on the brick wall. Walk all the was to the left of the brick wall and jump to the roof infront of Player 1. THen lunge at him through the invisable walls and you will be ontop! I appologize for this explination, it is EXTREAMLY hard to explain.

 

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