the other week i managed to get to round 51 without the use of traps , this was done by using just ray gun and ice gun Which did nothing after round 40+ . you must use the ice gun after rounds 30 + on the doctor this causes him to slow down there for easier to kill and get away. This was is a video of the game, sorry about the bad quility but i was all i had :/
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I would love to help anyone with the strategy.