Tower Relay: recover a route from a known stack checkpoint
A five-disc position after seven moves separates a harmless cancelled selection, a rejected placement and a legal detour that blocks the next planned disc.
Worked examples use the Standard board unless a different size is stated. Hard and Expert may change the board dimensions or amount of information to track.
Remember a position rather than a long click list
A long Tower Relay route is easier to review when you can recognise a few complete stack positions. A checkpoint need not be a game feature or saved file. It can be a position you describe to yourself, or write separately on paper, before continuing. The important information is each tower’s ordered discs, not merely the current move count.
Two different routes can use the same number of moves while leaving different stacks. Conversely, extra detours can revisit a familiar stack with a larger count. Treat the counter as a record of your current route, and use the visible disc order to decide whether the next planned move is actually available.
Recognise a concrete Hard-mode checkpoint
In the shortest five-disc transfer from Tower 1 to Tower 3, the first seven moves transfer the top three discs to Tower 3. At that checkpoint, Tower 1 contains discs 5 and 4 from bottom to top, Tower 2 is empty, and Tower 3 contains 3, 2 and 1. The next planned move is disc 4 from Tower 1 to Tower 2.
You can recognise why this move is now possible without remembering the seven earlier clicks. Disc 4 is exposed, and its destination is empty. Moving it makes room for the next stage of the transfer. If your board does not have those stacks, the fact that its counter also says seven is insufficient evidence that you have reached the same checkpoint.
Distinguish three kinds of interrupted move
Consider each action independently from that checkpoint, with no source already selected. Selecting Tower 3 and then selecting Tower 3 again cancels its source selection. No disc has moved. Trying to put disc 4 from Tower 1 onto Tower 3 is rejected because that tower’s top disc is smaller. Again, the stacks and move count remain unchanged. You can reconsider either action without needing Undo.
A different interruption is legal: move disc 1 from Tower 3 to Tower 1. The board accepts it and adds a move, but disc 1 now sits above disc 4 and blocks the planned transfer to Tower 2. The game reports no illegal placement because the detour respected its rules. Legal movement and useful preparation are separate questions.
Recover the reasoning along with the stack
Undo once after that detour restores the known checkpoint: 5, 4 on Tower 1, nothing on Tower 2, and 3, 2, 1 on Tower 3. It also returns the current route count from eight to seven. You may now move disc 4 to Tower 2 as originally intended. The counter has been restored; it is not a lifetime total of every physical click you have made.
If several moves followed an uncertain decision, reverse them one at a time while checking the stacks. Do not assume that a particular counter value guarantees recovery. Restart is available when reconstructing the route becomes more confusing than beginning again, but it does not preserve an in-game checkpoint. There is no penalty for taking a longer valid route; the purpose of a checkpoint is to restore a plan you understand.
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