C# for Game Dev: Unity Intro

After this lesson, you will be able to: Get oriented in Unity: MonoBehaviour, Update vs FixedUpdate, GameObjects + Components.

Unity is the most-used game engine + C# is its scripting language. This lesson is a SURVEY, just enough to make Unity approachable when you sit down with it.

Prerequisites:Entity Framework Core

Why C# devs care about Unity

Unity is THE indie game engine. Also used in films, AR/VR, sims, training, architectural visualization. C# is the scripting language (Unity also has visual scripting, but C# is the primary). If you want to build games or AR/VR + you already know C#, Unity is a low-friction next step.

MonoBehaviour — the script base class

Every Unity script inherits from MonoBehaviour. Attached to GameObjects.

tsx

using UnityEngine;

public class PlayerController : MonoBehaviour {
    public float speed = 5f;     // editable in Unity Inspector
    private Rigidbody _rb;

    // Called once when scene starts
    void Start() {
        _rb = GetComponent<Rigidbody>();
    }

    // Called every frame (variable rate, 60+ Hz typically)
    void Update() {
        float h = Input.GetAxis("Horizontal");
        float v = Input.GetAxis("Vertical");
        transform.position += new Vector3(h, 0, v) * speed * Time.deltaTime;
    }

    // Called at fixed timestep (50 Hz), use for physics
    void FixedUpdate() {
        _rb.AddForce(Vector3.up * 9.8f);
    }

    // Called on collision
    void OnCollisionEnter(Collision other) {
        Debug.Log($"Hit {other.gameObject.name}");
    }
}

GameObjects + Components

GameObject = container. Has a Transform (position/rotation/scale) + zero or more Components. Components = pieces of behavior. Renderer (visuals), Rigidbody (physics), Collider (collision), AudioSource (sound), your custom MonoBehaviour scripts. Composition over inheritance, add the components you need, swap them at runtime.

Update vs FixedUpdate vs LateUpdate

Update: every rendered frame. Variable rate. Use for input, animation, camera following. Multiply by Time.deltaTime for frame-rate-independent motion. FixedUpdate: every 0.02s (50 Hz) by default. Use for physics + Rigidbody operations. LateUpdate: after all Updates. Use for camera follow (so it tracks the player AFTER the player moved).

Common mistakes

Doing physics in Update instead of FixedUpdate (frame-rate-dependent behavior). Forgetting `* Time.deltaTime` in Update (different speeds on different machines). GetComponent in Update (slow, cache in Start). Direct transform.position changes on a Rigidbody (breaks physics, use rb.MovePosition).

←Entity Framework Core

Back to C# and .NET

Testing in C#→