Scripting & Gameplay

Most engines support scripting languages for gameplay code:

• Unity: C#.
• Unreal: C++ + Blueprints (visual).
• Godot: GDScript (Python-like) + C#.
• GameMaker: GML.
• Cocos2d: JS / Lua.
• Custom: Lua, Python embedded.

Why scripting?

• Faster iteration (no recompile of engine).
• Designer-friendly.
• Hot reload.
• Sandboxing.

Scripting interfaces:

• Components written in script attached to entities.
• Lifecycle hooks: Start, Update, OnCollide, OnDestroy.
• Engine API exposed: GetComponent, Instantiate, Destroy.

Example Unity-style:

public class Player : MonoBehaviour {
    public float speed = 5f;

    void Update() {
        if (Input.GetKey(KeyCode.LeftArrow))
            transform.position += Vector3.left * speed * Time.deltaTime;
    }

    void OnCollisionEnter(Collision col) {
        if (col.gameObject.tag == "Enemy")
            health.TakeDamage(10);
    }
}

Implementation: engine calls Update() on every script per frame. Reflection finds methods.

Hot reload:

• Recompile script while game runs.
• Re-attach script to existing entities.
• Useful for fast tweak cycles.
• Hard for state-altering changes; engine needs careful reload.

Visual scripting:

• Drag-and-drop nodes.
• Unreal Blueprints, Unity Visual Scripting, Godot Visual Script.
• Pros: artists/designers without code skills.
• Cons: hard to maintain large logic; performance worse than text.

Game state machines:

• Common pattern for AI, character states.
• States: Idle, Walking, Running, Jumping, Falling, Attacking.
• Transitions on events.
• Each state has Update + OnEnter + OnExit.

Behavior trees:

• Hierarchical AI.
• Common in modern AAA AI.
• Nodes: sequence, selector, parallel, decorator, leaf.

For our toy:

• Components are Python classes.
• Game logic is Python.
• Hot reload: re-import module, replace classes.

Modding:

• Allow user scripts.
• Python or Lua for sandbox.
• Skyrim, Minecraft, Civ are heavily modded.
• Need: API, sandbox, mod loader.