Working with the UI Source - Unity 3D UI Essentials - page 213

You don't have to build an input system if you don't want to; this is just one
example. If you wish you can simply call ExecuteEvents.Execute (provided you
have a reference to the Event System from the scene) from anywhere in your code to
fire an event, say for a Game Over event maybe!
The Roll a Ball Derby
If we take the previous system and put it into action in a simple example, we can
start to see the possibilities of the new UnityEvent system.
For this, I used Unity's own Roll a Ball example from their tutorial
site, which you can follow along to create the base sample: http://
unity3d.com/learn/tutorials/projects/roll-a-ball .
To save time (and since Unity doesn't provide a finished version of the
tutorial) I've created a Unity package you can import to speed along its
creation, which you can download from http://bit.ly/1AaDKF2 and
then import into your project using Assets | Import Package | Custom
Package in the menu. (It's also included in the code bundle for this project
in the Chapter 6 folder).
In the Roll A Ball example, we start off with a simple scene where our valiant hero
ball is completely surrounded, as you can see in the following screenshot:
The completed Roll A Ball Unity tutorial (without the GUIText parts)