Duck Survival DBUpgrade the breach, not every tower
Watch where your defense breaks first.
A summary of BlueStacks editorial advice, not an official efficiency formula or our own combat measurement.
What to check
The French BlueStacks guide recommends concentrating upgrades around the point enemies actually break through, rather than spreading small upgrades everywhere.
Control effects can give nearby damage more time to work. Compare the result on your stage; this is a tactical suggestion rather than a tested ranking of every tower.