Fifteen spaces must hold thirteen groups: four aces together, four twos together, and so on through kings. The deck is all visible, with two empty spaces at the start.
Match ranks, not suits
Move only an exposed card. An occupied pile accepts the same rank as its exposed card, provided the pile contains fewer than four cards. An empty space accepts any card. There are no foundations, hidden cards or stock draws; win when every occupied pile contains four cards of one rank.
Use an empty space to gather a rank that is blocking several other cards. Avoid filling both spaces with unrelated cards that cannot soon move away. When two matching cards can receive the same blocker, choose the destination that keeps access to the other ranks beneath it.