Start with a rule you can see
A good puzzle makes its rules legible before it asks you to combine them. In Arrow Flow, a path either has room to leave or it does not. The player should be able to predict that result from the board.
Difficulty can come from the number of relationships between paths, without hiding information or changing the rules halfway through a move.
Make a mistake useful
When a move fails, the response should explain why. A clear blocked path teaches more than a vague failure message. The next attempt should feel more informed.
That is also why a solvable board matters. If a player gets stuck, they should be able to trust that there is a route forward.
Give the player room to think
A small puzzle can be a quiet daily ritual. An easy opening, a more demanding middle and a satisfying final move can give a board its own rhythm.
More complexity is not always more fun. Watching where players hesitate—and listening when they tell us why—is part of finding the right balance.