The secret to become top ten in survival mode? Turret is the first priority rather soldier. I take running and crusader perk, Use helicopter 2500$ while surviving until wave 16. Once you maximize turret, have the best helicopter, the best 3 soldier and then Wolaaaa. You can sit at center, left it idle there, let the soldier and air support do their job and you can go rest because its gonna take an hour before reaching 15k++. Just take a peak a while to restore your air support. I can start relax when i reach 6k kill and when i check again, i die when i reach 15k++ kill
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