How in the world is this game even slightly possible? The previous game was very doable, and yet strangely huge amounts more people have the medals in this game than in that one. I can't even get past a few rounds in this one, no matter what the map or the strategy.
Also most of the people with all the medals in this game aren't particularly good at games, which leads me to believe either they played an earlier, much easier version of the game, that they found some glitch in the game to win (I do see mention of a fixed 6000 credits glitch in the comments so maybe that's it), that they cheated, or that this thing somehow performs vastly differently on different computers and maybe is only possible to win in certain OS/browser combinations.
It also seems fairly arbitrary where you can or cannot put a turret as sometimes it won't let you but within a pixel or two of that spot is okay, etc...
Also doesn't help that all your turrets have the exact worst strategy possible -- keep attacking whatever you were attacking (and failing to kill) and thus always continue to fail by attacking exclusively the tail-end rather than doing it smartly by focusing more on the front-end.
Hell it would be better if these turrets didn't turn at all and you just positioned them permanently at the start and whatever direction you initially put them in they're stuck that way.