⚙️ How Unity “Talks” to Your Code

You’ve learned how to write scripts.
Now let’s learn how Unity knows when and how to run your code.

In Unity, there are special built-in methods — like Start(), Update(), and OnCollisionEnter() — that Unity calls automatically at specific times.

This is made possible through MonoBehaviour, Unity’s magical base class that connects your scripts to the engine.

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👑 What is MonoBehaviour?

All your Unity scripts inherit from this class:

public class MyScript : MonoBehaviour
{
    // Magic lives here
}

By inheriting from MonoBehaviour, Unity can call special methods like Start() and Update() without you needing to do anything else.

🧙 Think of MonoBehaviour as the wizard behind the curtain that hooks your code into the game loop.

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🚀 Start() – Runs Once

void Start()
{
    Debug.Log("The game has started!");
}

• Called once at the very beginning (when the object becomes active)
• Great for initialization, setting values, or printing welcome messages
• Happens before the first Update()

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🔁 Update() – Runs Every Frame

void Update()
{
    Debug.Log("Still running...");
}

• Called every frame — 60+ times per second depending on your hardware
• Ideal for real-time logic like:
  • Player input
  • Moving objects
  • Checking timers

💡 Too much heavy stuff in Update() = lag town. Use wisely.

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🧪 Example Script

using UnityEngine;

public class HelloUnity : MonoBehaviour
{
    void Start()
    {
        Debug.Log("Game started");
    }

    void Update()
    {
        Debug.Log("Frame running...");
    }
}

Attach this script to a GameObject, hit play, and check the Console:
You’ll see “Game started” once, and “Frame running…” repeatedly.

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🛠️ Other Useful MonoBehaviour Methods

Method	When it Runs
Awake()	Before Start() (used for internal setup)
FixedUpdate()	Called at fixed intervals (physics-related)
OnCollisionEnter()	When object collides with another
OnTriggerEnter()	When trigger collider is entered
OnDestroy()	When the object is removed from the scene

We’ll explore these more in future lessons. For now, Start() and Update() are your go-to tools.

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🧠 Recap

• MonoBehaviour connects your code to Unity’s event system
• Start() runs once when the object activates
• Update() runs every frame (use it for live logic)
• These methods let your scripts become interactive parts of the game world

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🧪 Mini Challenge: Frame Counter

1. Create a new script called FrameTracker.cs
2. In Update(), increase a counter every frame
3. Every 60 frames, print "One second-ish passed"
4. Reset the counter after logging

Bonus: Try printing a message every 5 seconds using a float timer instead!

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🚀 What’s Next?

Congrats, you’ve finished Section 2! 🎉
You now know the basics of variables, methods, logic, loops, and Unity’s script lifecycle.

Next up, we’ll build our very first game together — a classic clicker game to put your skills into action!

👆 Go to Section 3 → Your First Game – Clicker Game