When dealing with difficult puzzles, Daisy Sudoku allows several methods that can be used to make the solution easier.
It is a very good idea to save the puzzle after you have entered the fixed values. This means that if you make a complete mess, you can go back to the start.
Take the puzzle shown below which has come to a complete halt after the application of Auto-Solve.
This is because the solution is indirect or circular and you will have to resort to trial and error.
The process is very simple.
Choose one of the numbers in one of the unsolved cells, enter it and then click Auto-Solve. If the solution is incorrect, you will end up with the number twice in a box, row or column. It will be highlighted in red.
In that case just click Undo Solve and then replace the incorrect entry with another.