Provide a meaningful undo action

The problem

Puzzle players should recover from slips without restarting an entire session.

Practical procedure

Store the previous position and collectible state for each valid move; undo should restore both atomically.

Worked scenario

If a move collects the third cell, undo must restore that cell and the previous cell count.

Acceptance check

Run collect-undo-recollect sequences and compare the board state after every operation.

Apply the method

Use the related interactive tool to try the concept on an inspectable example. Record the starting assumptions and expected result before changing settings, then compare what the tool actually does. Where the result differs, keep the release marked experimental and document the discrepancy.

Further reading: Relevant primary technical documentation. This guide is an educational procedure, not a substitute for independent usability or compliance review.