Defining game logic, rules, and behavior often requires scripting. Specifically, to transform a static and lifeless scene with objects into an environment that does something, a developer needs to code behaviors. It requires someone to define how things should act and react under specific conditions. The coin collection game is no exception to this. In particular, it requires three main features:

There's no default out-of-the-box functionality included with Unity to handle this scenario. So we must write some code to achieve it. Unity supports two languages, namely, UnityScript (sometimes called JavaScript) and C#. Both are capable and useful languages, but this book uses C# because, going forward, support for JavaScript will eventually be dropped. Let's start coding these three features in sequence. To create a new script...

The coin collection game wouldn't really be much of a game if there were only one coin. The central idea is that a level should feature many coins, all of which the player should collect before a timer expires. Now, to know whether all coins have been collected, we'll need to know how many coins there are in total in the scene. After all, if we don't know how many coins there are, then we can't know if we've collected them all. So, our first task in scripting is to configure the Coin class so that we can know the total number of coins in the scene at any moment easily. Consider Code Sample 2.3, which adapts the Coin class to achieve this:

//-------------------------
using UnityEngine;
using System.Collections;
//-------------------------
public class Coin : MonoBehaviour 
{
  //-------------------------
  //Keeps track of total coin count in scene
  public static int CoinCount = 0;
  //-------------------------
  // Use this for initialization
  void...

Previously, we developed a coin counting variable telling us how many coins are in the scene. However, regardless of the count, the player still can't collect the coins during gameplay. Let's fix this now. To start, we need to think about collisions. Thinking carefully, we know that a coin is considered collected whenever the player walks into it, that is, a coin is collected when the player and the coin intersect or collide.

To determine when a collision happens like that, we must approximate the volume of both the player and coin in order to determine when the two volumes overlap in space. This is achieved in Unity through colliders. Colliders are special physics objects attached to meshes. They tell us when two meshes intersect. The FPSController object (First-person controller) already has a collider on it, through its Character Controller component. This approximates the physical body of a generic person. This can be confirmed by selecting FPSController in...

The basic coin functionality is now created, but the scene needs more than one coin. The problem with simply duplicating a coin and scattering the duplicates is that if we make a change later to one coin and need to propagate that change to all other coins, we'd need to delete the former duplicates and manually replace those with newer and amended duplicates. To avoid this tedious repetition, we can use prefabs. Prefabs let you convert an object in the scene to Assets in the Project panel. This can be instantiated in the scene as frequently as needed, as though it were a mesh asset. The advantage is that changes made to the asset are automatically applied to all instances automatically, even across multiple scenes.

This makes it easier to work with custom assets, so let's prefab the coin right now. To do this, select the Coin object in the scene and then drag and drop it in the Project panel. When this happens, a new prefab is created. The object in the scene...

You should now have a level complete with geometry and coin objects. Thanks to our newly added Coin.cs script, the coins are both countable and collectible. Even so, the level still poses little or no challenge to the player because there's no way the level can be won or lost. Specifically, there's nothing for the player to achieve. This is why a time limit is important for the game: it defines a win and loss condition. Namely, collecting all coins before the timer expires results in a win condition and failing to achieve this results in a loss condition. Let's get started at creating a timer countdown for the level. To do this, create a new and empty game object by selecting GameObject | Create Empty and rename this LevelTimer. See Figure 2.25:

Figure 2.25: Renaming the timer object

The coin collection game is nearly finished. Coins can be collected and a timer expires, but the win condition itself is not truly handled. That is, when all coins are collected before time expiry, nothing actually happens to show the player that they've won. The countdown still proceeds and even restarts the level as though the win condition hadn't been satisfied at all. Let's fix this now. Specifically, when the win scenario happens, we should delete the timer object to prevent further countdown and show visual feedback to signify that the level has been completed. In this case, I'll add some fireworks! So, let's start by creating the fireworks. You can add these easily from the Unity Particle System packages. Navigate to the Standard Assets | ParticleSystems | Prefabs folder. Then, drag and drop the Fireworks particle system in Scene.

Add a second or even a third one if you want:

Figure 2.29: Adding two Fireworks prefabs

By default,...