i made the absolutely longest road i could, going back and forth left and right. it took a while. then i put some turret in... on the far side so i had to wait a very long time.
did not immediately know that i needed to fire the turrets myself, but as the first wave was only two, i took them out quite readily.
even after a few more waves, bunching up a bunch of turrets seemed to keep them under control, but tower defense games are notoriously hard to balance.
the game is pretty solid.