@chrisamaphone so I figured dusa should be good for solving some kinds of puzzles, like bridges, right?
Tried to draw a trivial one (https://tinyurl.com/4w52su5y), without any bridge crossings to worry about -- but I can't seem to say "the total number of bridges on an island should not exceed the defined limit".
Am I holding it wrong, or is this not possible on a fundamental level?