The probability of winning Thoughtful Klondike (with draw three rules) has been calculated as being approximately 82%, more precisely as having a confidence interval of 81.956% ± 0.096%. Thoughtful Klondike is not quite the same as simply playing with all cards face up, as this would allow an impossible movement of a pile if the top downturned card happened to be in sequence with the upturned card underneath it. Using physical cards, Thoughtful Klondike can be played by peeking at the face-down cards, while with electronic programs Thoughtful Klondike can be played by allowing unlimited use of undos to return to the start if a choice turns out to be unfavourable.