Consider the following game-state in Spider Solitaire. Although this game is not the most popular compared to others (e.g. poker, chess, backgammon etc) I assume the reader is familiar with the basic ruleset which is easily found online. I assume Joe Bloggs is playing at the four-suit level and is not allowed to undo moves.
(1) How many face-down cards is Joe guaranteed to turn over before being forced to deal another row of 10 cards, even if the worst possible cards turned up?
(2) How many face-down cards can Joe turn over if every face-down card is a cow? Cows can only move to empty columns and nothing can move onto a cow.
(3) Your answers to (1) and (2) should be the same. Can you construct a game state where they are different? To discourage trivial solutions let us say the "best" example is one with highest number of unknown cards (either face-down in the tableau or in the stock).