Here’s a crash course in designing for touch screen games. In it you will learn how to think about your players and the limits that they have when playing your games. A game designer must always be aware of what device a player will be using as well as the environment they will be interacting with. A board game design is very different from a console game, not only because of the medium through which it is played (cardboard vs silicone) but also the environment you are in (around a table with friends vs on a couch on your own).
Touchscreen devices are present with us all the time, carried in your pocket. However, people play games in different ways, sometimes for a brief minute or more and at other times on a couch with a 20 minute gameplay session. In each instance you should try to think how your players will play your games and design appropriate:
Read each step in order, to learn how mobile game design is different from other mediums:
Step 1: Understand the environments that your players are playing in. Understand their limitations.
Step 2: A list of all the different interaction methods on a touch screen, and when to use each one.
Step 3: Some rules of thumb when designing a touch mechanic, like ensure there is only one mechanic running at time.