What is Random deal?
Every standard game here is dealt so that it can be cleared. The deal is built backwards: matching pairs are placed on positions that would be free in turn, so at least one order of moves takes every tile off, and getting stuck always means a choice that could have been made better.
The random deal drops that guarantee. The faces are shuffled and laid on the positions with no check at all. Most deals can still be cleared, but some cannot, however well you play: for example, when the four tiles of one kind are stacked in a single pile, or when two pairs each cover the other's partner.
Play a random deal for the classic challenge, where a lost game may be the deal's fault rather than yours. Shuffles are a good match for it: a shuffle deals the faces left the solvable way, which can rescue a board that had no way through.
Rule changes
| Rule | Standard Mahjong Solitaire | Random deal |
|---|---|---|
| Deal | Standard Mahjong SolitaireBuilt backwards from pairs on positions that would be free in turn. | Random dealThe faces are shuffled and laid on the positions at random. |
| Can it be cleared? | Standard Mahjong SolitaireAlways, with the right order of moves. | Random dealNot always: some deals have no solution. |
| Getting stuck | Standard Mahjong SolitaireMeans an earlier choice could have been better. | Random dealMay mean the deal had no way through from the start. |
| Other options | Standard Mahjong SolitaireAny layout, shuffles and a time limit can be chosen in the setup. | Random dealThe random deal works on every layout, with shuffles and with a time limit. |
History
A deal made by laying the tiles out at random may have no solution. One analysis of ten million random deals of the Turtle found that about 3 percent cannot be cleared even by a player allowed to look under the tiles. Deciding whether a deal can be cleared is also hard for a computer: with every tile visible, the problem is NP-complete.
Many versions deal only boards that can be won, and that is the standard game here. The random deal brings back the uncertainty.