I got to level 42. there is a simple thing to do. Around round 15 you should open the door to the cat walk in the back by the teleporter. Kill some guys but when it gets to be too much have a partner throw a monkey then jump down to the teleporter (that should be linked!) and teleport when needed. hen run by the trench gun way up the stairs and hang out by where you fall off the wall . Camp and ill until zombies come across the bridge or to many zombies come. Then jump donw and turn the fence on and watch the zombies be zapped return to the catwalk and do it over and over as much needed. LEVEL 42 PEOPLE!