Try to build a house of cards. Make sure the foundations and lower layers are strong enough to support higher layers. Walls are pairs of the same value or suit. Roofs can be any card. Walls of 20 and 21 in value have special capabilities.
Every level a freecell less and more difficult to solve. Move all the cards to the four foundations on color from Ace to King. On the tableau build down in alternating color. You can temporarily place a card on a Free Cell (if available).