Many mobile games have a single input whereby you can tap anywhere on the screen to make an action happen. For example, endless runners tend to allow the player to tap or press and hold anywhere on the screen to jump. To achieve this, you only have to add an invisible button that covers the whole screen. If you have another UI that receives inputs, it needs to be in front of the full-screen button so that the button does not block the inputs to the other UI items.

Some games require that you tap on specific regions of the screen to perform specific actions. For example, I created a game called Sequence Seekers for my doctoral dissertation. This game included a down-the-mountain mode in which the player had to tap the left or right-hand side of the screen to move left or right in the game. I achieved this by adding invisible buttons that covered the two halves of the screen, as shown here:

Figure 2.14: Using invisible buttons...