The puzzle generator has more cunning

In version 2.4.0, ​the puzzle generator has more cunning and deleted combinations are restored when steps are undone. The changes in detail:

• More logic has been built into the puzzle generator, making it possible for it to generate puzzles that are even more challenging to solve! The new logic is used in Advanced and Expert play modes.
• When the Undo button is used to back-track the steps that have been played, any combinations that were deleted individually are now restored on a step-by-step basis. The same also applies when the help option “undo back to where I went wrong” is used. The ability to delete individual combinations is an optional feature that can be turned on in the settings.
• Some of the help explanations have been improved.