Why every puzzle has one solution
Every DIGIGMA puzzle has one solution. There is one way to finish the grid. If a mark is right, it is the only mark that can sit there.
That is a fact of the product, not a slogan. The site does not hand you a board that can end two ways.
Uniqueness is what makes guessing feel worse. If you place a mark that is not forced, you are not exploring options. You are leaving the only path.
When you are stuck, the next mark is already on the board, waiting. Look again. The how-to for Sudoku, Star Battle, and Binary Puzzle names the first scans that find it.