First Unity project (Hello World scene) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Unity C# script?

Consider this simple Unity script attached to a GameObject. What will be printed in the Console when you run the scene?

Unity

using UnityEngine;

public class HelloWorld : MonoBehaviour
{
    void Start()
    {
        Debug.Log("Hello, Unity World!");
    }
}

A Hello, Unity World!

B Error: Debug.Log is undefined

C Nothing is printed

D Hello World

💡 Hint

Look at what Debug.Log prints inside the Start method.

The Start method runs once when the scene starts. Debug.Log prints the exact string to the Console, so it prints "Hello, Unity World!".

🧠 Conceptual

intermediate

Which Unity method runs exactly once when the scene starts?

In Unity scripts, which method is called automatically once when the scene begins?

A FixedUpdate()

B Update()

C Start()

D Awake()

💡 Hint

Think about the method that runs after all Awake methods but before the first frame.

Start() is called once before the first frame update. Awake() runs earlier but also once. However, Start() is the common method to initialize things when the scene starts.

🔧 Debug

advanced

Why does this script not print anything in the Console?

Look at this script attached to a GameObject. Why does it not print "Hello World" when the scene runs?

Unity

using UnityEngine;

public class HelloWorld : MonoBehaviour
{
    void start()
    {
        Debug.Log("Hello World");
    }
}

A The method name should be capitalized as Start() to be called by Unity.

B Debug.Log cannot print strings, only numbers.

C The script must inherit from ScriptableObject, not MonoBehaviour.

D The GameObject is inactive, so scripts never run.

💡 Hint

Unity calls specific methods by exact names and capitalization.

Unity calls the Start() method with capital S automatically. The method named start() with lowercase s is ignored, so nothing prints.

📝 Syntax

advanced

Which option fixes the syntax error in this Unity C# script?

This script has a syntax error. Choose the option that fixes it so it compiles and prints "Hello World".

Unity

using UnityEngine;

public class HelloWorld : MonoBehaviour
{
    void Start()
    {
        Debug.Log("Hello World"
    }
}

A Remove the semicolon after Debug.Log("Hello World")

B Change Debug.Log to Debug.Print("Hello World");

C Add a return type int to Start method: int Start()

D Add a closing parenthesis after the string: Debug.Log("Hello World");

💡 Hint

Check if all parentheses and semicolons are correctly placed.

The Debug.Log call is missing a closing parenthesis and semicolon. Adding them fixes the syntax error.

🚀 Application

expert

How many GameObjects are created after running this script?

This script creates new GameObjects in the scene. How many GameObjects exist after Start() finishes?

Unity

using UnityEngine;

public class CreateObjects : MonoBehaviour
{
    void Start()
    {
        for (int i = 0; i < 3; i++)
        {
            GameObject obj = new GameObject($"Object_{i}");
        }
    }
}

A 3 GameObjects named Object_0, Object_1, Object_2

B 4 GameObjects including the one with this script attached

C 1 GameObject named Object_2 because previous are overwritten

D 0 GameObjects because new GameObject() does not add to scene

💡 Hint

Remember the original GameObject with this script plus the new ones created.

The script creates 3 new GameObjects plus the original GameObject that has this script attached, so total 4 GameObjects exist.

Practice

1. What is the main purpose of creating a Hello World scene in your first Unity project?

easy

A. To display a simple message on the screen and learn basic Unity setup

B. To create a full game with levels and enemies

C. To design complex 3D models

D. To write advanced shaders for graphics

Solution

1. Step 1: Understand the goal of a first Unity project

   The first project is usually simple to help beginners learn the basics of scenes and UI.

2. Step 2: Identify what a Hello World scene does

   It shows a simple message like "Hello World!" on screen to confirm everything works.

3. Final Answer:

   To display a simple message on the screen and learn basic Unity setup -> Option A

4. Quick Check:

   First project = simple message display [OK]

Hint: First project means simple message, not full game [OK]

Common Mistakes:

• Thinking Hello World is a full game
• Confusing UI design with 3D modeling
• Trying to write shaders too early

2. Which of the following is the correct way to display "Hello World!" text using TextMeshPro in Unity C# script?

easy

A. textMeshProUGUI.text = Hello World!;

B. textMeshProUGUI.setText("Hello World!");

C. textMeshProUGUI.text = "Hello World!";

D. textMeshProUGUI.text = 'Hello World!';

Solution

1. Step 1: Recall correct syntax for assigning string in C#

   Strings must be in double quotes and assigned with = operator.

2. Step 2: Check TextMeshPro property usage

   The correct property to change text is .text, so textMeshProUGUI.text = "Hello World!"; is correct.

3. Final Answer:

   textMeshProUGUI.text = "Hello World!"; -> Option C

4. Quick Check:

   Assign string with .text and double quotes [OK]

Hint: Use .text with double quotes for strings in C# [OK]

Common Mistakes:

• Using single quotes for strings in C#
• Missing quotes around Hello World!
• Using a non-existent setText method

3. Given this Unity C# script attached to a GameObject with a TextMeshProUGUI field linked:

using TMPro;
using UnityEngine;

public class HelloWorld : MonoBehaviour {
    public TextMeshProUGUI messageText;
    void Start() {
        messageText.text = "Hello World!";
    }
}

What will appear on the screen when you run the scene?

medium

A. The text "messageText" will appear instead

B. Nothing will appear because Start() is not called

C. A compile error due to missing semicolon

D. The text "Hello World!" will appear on the UI

Solution

1. Step 1: Understand the Start() method in Unity

   Start() runs once when the scene starts, so the text assignment happens immediately.

2. Step 2: Check the text assignment

   The script sets messageText.text to "Hello World!", so that exact text will show on the UI.

3. Final Answer:

   The text "Hello World!" will appear on the UI -> Option D

4. Quick Check:

   Start() sets text to "Hello World!" [OK]

Hint: Start() runs once, sets text to Hello World [OK]

Common Mistakes:

• Thinking Start() does not run automatically
• Confusing variable name with displayed text
• Assuming compile error without checking code

4. You wrote this script to show "Hello World!" but the text does not appear:

using TMPro;
using UnityEngine;

public class HelloWorld : MonoBehaviour {
    public TextMeshProUGUI messageText;
    void Start() {
        messageText.text = "Hello World!";
    }
}

What is the most likely reason the text is not showing?

medium

A. The messageText variable should be private

B. The TextMeshProUGUI field is not linked to the UI text in the Inspector

C. The Start() method is misspelled

D. The script is missing a semicolon after the text assignment

Solution

1. Step 1: Check common reasons for UI text not updating

   If the public field is not linked in Inspector, messageText is null and text won't show.

2. Step 2: Verify code correctness

   The code syntax is correct, Start() is spelled right, and variable privacy does not affect linking.

3. Final Answer:

   The TextMeshProUGUI field is not linked to the UI text in the Inspector -> Option B

4. Quick Check:

   Unlinked UI field = no text shown [OK]

Hint: Always link public UI fields in Inspector [OK]

Common Mistakes:

• Assuming syntax errors without checking code
• Thinking private variables must be used
• Ignoring Inspector linking step

5. You want to create a Hello World scene that changes the text to "Welcome!" when the user clicks a button. Which approach correctly combines UI and scripting in Unity?

hard

A. Create a public method in a script that sets the TextMeshProUGUI text, then link this method to the button's OnClick event

B. Write code in Start() to change text and expect it to update on button click automatically

C. Change the button text directly without scripting

D. Use Update() method to constantly set text to "Welcome!"

Solution

1. Step 1: Understand how button clicks trigger actions

   Unity buttons use OnClick events to call public methods in scripts.

2. Step 2: Identify correct way to change UI text on click

   Write a public method that sets the TextMeshProUGUI text to "Welcome!" and link it to the button's OnClick.

3. Final Answer:

   Create a public method in a script that sets the TextMeshProUGUI text, then link this method to the button's OnClick event -> Option A

4. Quick Check:

   Button OnClick calls public method to change text [OK]

Hint: Use button OnClick to call public method changing text [OK]

Common Mistakes:

• Expecting Start() to handle button clicks
• Changing button text instead of target text
• Using Update() unnecessarily causing performance issues