Coffee Roaster is a solitaire pool-building game.
You choose a variety of coffee beans you want to roast, and put a number of tokens specific to that variety into a bag. Each turn, you draw a number of bean tokens randomly from the bag to advance their roast level.
When you are finished, you make a cup-testing to check the taste of your coffee and score points accordingly.
Each variety has its own target roast level, but approaching the target is not enough for perfect roasting; you also have to even out the roast level of each bean, while not spoiling the flavor of that variety.