In Yak, the village elder has given you (and others) the task of constructing a great stone tower to guide the merchants and their yaks in the Himalayas. Each turn, a yak pulls its cart into your village. Will you find stones for your tower, or food for your reserves? Or will you need to visit the market to find what you need?

Over the course of the game, each player builds their own stone tower by acquiring stones from visiting merchants. You start the game with one good of each type (meat, milk, bread) and three cards in hand: build, restock, and market. Three or four carts being pulled by yaks start on the game board, with each player having one cart in front of them and each cart containing three stones and some food.

To end a round, return your chosen card to your hand, move the yak carts one space in the direction they face, then pass the baby yak clockwise. Continue playing rounds until someone completes the fourth level of their tower. Complete that round, play one additional round, then score the towers. A crystal stone can be a color of your choice, but each crystal in your tower must be a different color. You score points (1) for each group of two or more stones (e.g., a group of six is worth 16 points), (2) for the number of groups of at least two or more stones, (3) for individual stones (only 1 point each), (4) for triggering the end of the game, and (5) for having the most remaining food.