Build a Complete Game Using C#

# CHAPTER 20

Build a Complete Game Using C# #

1. Introduction #

2. Project Requirements #

• Player: A character that moves via WASD and aims/shoots via the Mouse.

• Combat: A gun that utilizes Object Pooling to shoot projectiles.

• Enemy AI: Zombies that use NavMesh pathfinding to chase the player.

• Game Manager: A system to handle waves of enemies and score.

• UI: A Canvas showing Health, Score, and Ammo.

• Persistence: A JSON save system to record the highest wave survived.

3. Step 1: Core Architecture and Singletons #

1. 1. Create a GameManager (Singleton) to track currentScore and currentWave.

1. 2. Create an AudioManager (Singleton) to handle SFX routing without destroying audio sources.

1. 3. Create a UIManager (Singleton) that listens for C# Events to update the Canvas.

4. Step 2: The Player Controller #

• PlayerMotor.cs: Reads Input.GetAxis for WASD. Reads Mouse position using a Raycast to make the character rotate and face the cursor. Applies Time.deltaTime movement.

• PlayerHealth.cs: Holds maxHealth. Has a public TakeDamage(int) method. Broadcasts an Action<int> event when health drops, which the UIManager listens to.

• WeaponController.cs: Listens for Input.GetMouseButtonDown(0). Requests a bullet from the Object Pool and applies velocity to it.

5. Step 3: Object Pooling the Projectiles #

1. 1. Create a BulletPool.cs script.

1. 2. In Awake(), instantiate 50 bullet Prefabs and SetActive(false).

1. 3. When the WeaponController fires, it calls BulletPool.Instance.GetBullet().

1. 4. The bullet moves forward using FixedUpdate.

1. 5. When the bullet hits an enemy (detected via OnTriggerEnter), it subtracts health and calls SetActive(false) to return itself to the pool.

6. Step 4: The Enemy AI State Machine #

• Attach a NavMeshAgent component to the Zombie.

• ZombieAI.cs: Create an enum State { Chase, Attack, Dead }.

• In the Update loop, if Chase, set the NavMesh destination to the Player's transform.

• If the distance to the player is < 2.0f, switch to Attack state and trigger the attack animation via the Animator component.

• EnemyHealth.cs: When health hits 0, switch to Dead state, disable the collider, play the death animation, and tell the GameManager to add 100 points to the score.

5. Step 5: Wave Spawning System #

• Create a WaveSpawner.cs script.

• Use a Coroutine (IEnumerator) to spawn enemies.

IEnumerator SpawnWave()
{
    int enemiesToSpawn = currentWave * 5;
    for (int i = 0; i < enemiesToSpawn; i++)
    {
        // Pick a random spawn point
        Instantiate(zombiePrefab, randomSpawnPoint.position, Quaternion.identity);
        yield return new WaitForSeconds(1.5f); // Wait 1.5s between spawns
    }
}

6. Step 6: Visual Polish (Juice) #

• In WeaponController, instantiate a Muzzle Flash particle system when firing.

• In PlayerCamera, write a Coroutine that applies "Screen Shake" by rapidly shifting the camera's X/Z coordinates for 0.2 seconds when the player takes damage.

• Use AudioSource.pitch = Random.Range(0.8f, 1.2f) for the gunshot sound to prevent audio fatigue.

7. Step 7: Saving the High Score #

• Create a SaveData.cs class marked with [System.Serializable].

• Include public int highestWave; and public int highestScore;.

• When the Game Over screen triggers, check if the current score is greater than the saved score.

• If true, use JsonUtility.ToJson() to serialize the data and File.WriteAllText() to save it to Application.persistentDataPath + "/save.json".

8. The Final Playtest #

1. 1. Hit Play.

1. 2. Move via WASD, aim with the mouse. The movement is framerate-independent due to deltaTime.

1. 3. Shoot the approaching zombies. The bullets do not cause lag because of Object Pooling.

1. 4. Watch the UIManager dynamically update the health bar without being directly linked to the Player script.

1. 5. Survive as many waves as possible until the game saves your high score via JSON.

9. Your Journey Continues #

C# is now a tool firmly in your grasp. From here, the path is yours. Participate in Game Jams (like Ludum Dare) to force yourself to build small games rapidly under pressure. Read the official Unity or Godot Documentation. Dive into advanced topics like multiplayer Netcode or DOTS architecture.

Game development is a journey of lifelong learning, problem-solving, and creativity. You have the language. You have the knowledge. Now go build the game you've always dreamed of playing.

Course Complete.