The pleasure of a unique solution
When a puzzle has one solution, every right mark is inevitable. You are not choosing among endings. You are finding the only one.
That is a calm kind of pleasure. The board agrees with you, or it does not. There is no audience and no other grid hiding in the clues.
You feel it most on the last few cells: the remaining marks fall out, and the rules hold. The puzzle is solved.
Sudoku, Star Battle, and Binary Puzzle are built this way. That is why guessing feels like leaving the work, and why sitting with a stuck cell is the real sit.