Collider2D types (box, circle, polygon) in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a BoxCollider2D component to the GameObject.

Unity

gameObject.AddComponent<[1]>();

Drag options to blanks, or click blank then click option'

ACircleCollider2D

BBoxCollider2D

CPolygonCollider2D

DRigidbody2D

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing CircleCollider2D or PolygonCollider2D instead of BoxCollider2D.

The BoxCollider2D component adds a box-shaped collider to the GameObject.

2fill in blank

medium

Complete the code to add a CircleCollider2D component and set its radius to 2.5.

Unity

var collider = gameObject.AddComponent<[1]>(); 
collider.radius = 2.5f;

Drag options to blanks, or click blank then click option'

ACircleCollider2D

BPolygonCollider2D

CEdgeCollider2D

DBoxCollider2D

Attempts:

3 left

💡 Hint

Common Mistakes

Using BoxCollider2D which does not have a radius property.

The CircleCollider2D component adds a circular collider, and the radius property sets its size.

3fill in blank

hard

Fix the error in the code to add a PolygonCollider2D component.

Unity

PolygonCollider2D collider = gameObject.AddComponent<[1]>();

Drag options to blanks, or click blank then click option'

ACircleCollider2D

BBoxCollider2D

CCapsuleCollider2D

DPolygonCollider2D

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different collider type name that does not match the variable type.

The PolygonCollider2D component is added using its exact type name inside the AddComponent<> method.

4fill in blank

hard

Fill both blanks to create a BoxCollider2D and set its size to (5, 4).

Unity

var collider = gameObject.AddComponent<[1]>(); 
collider.size = new Vector2([2], 4);

Drag options to blanks, or click blank then click option'

ABoxCollider2D

BCircleCollider2D

CPolygonCollider2D

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using CircleCollider2D which does not have a size property.

Setting size with wrong values.

Use BoxCollider2D to add the box collider, and set the size property with a Vector2 where the width is 5 and height is 4.

5fill in blank

hard

Fill the two blanks to add a PolygonCollider2D, set its path count to 1, and define a triangle shape.

Unity

var collider = gameObject.AddComponent<[1]>(); 
collider.pathCount = [2]; 
collider.SetPath(0, new Vector2[] { new Vector2(0,0), new Vector2(1,0), new Vector2(0,1) });

Drag options to blanks, or click blank then click option'

ABoxCollider2D

B1

CPolygonCollider2D

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using BoxCollider2D instead of PolygonCollider2D.

Setting pathCount to wrong number.

Use PolygonCollider2D to add the polygon collider, set pathCount to 1 to define one shape, and use SetPath to set the triangle points.

Practice

1. Which Collider2D type is best suited for a rectangular game object in Unity?

easy

A. BoxCollider2D

B. CircleCollider2D

C. PolygonCollider2D

D. EdgeCollider2D

Solution

1. Step 1: Understand the shape of the object

   A rectangle or square has straight edges and right angles.

2. Step 2: Match the collider type to the shape

   BoxCollider2D fits rectangles and squares perfectly because it creates a box-shaped collision area.

3. Final Answer:

   BoxCollider2D -> Option A

4. Quick Check:

   Rectangle shape = BoxCollider2D [OK]

Hint: Rectangles use BoxCollider2D for perfect fit [OK]

Common Mistakes:

• Choosing CircleCollider2D for rectangles
• Using PolygonCollider2D unnecessarily for simple shapes
• Confusing EdgeCollider2D with BoxCollider2D

2. Which of the following is the correct way to add a CircleCollider2D component to a GameObject in C# script?

easy

A. gameObject.AddComponent<BoxCollider2D>();

B. gameObject.AddComponent<PolygonCollider2D>();

C. gameObject.AddComponent<CircleCollider2D>();

D. gameObject.AddComponent<EdgeCollider2D>();

Solution

1. Step 1: Identify the correct component type

   CircleCollider2D is the component for circular collision shapes.

2. Step 2: Use AddComponent with the correct type

   The syntax is gameObject.AddComponent<Type>(); so for circle, use CircleCollider2D.

3. Final Answer:

   gameObject.AddComponent<CircleCollider2D>(); -> Option C

4. Quick Check:

   Add CircleCollider2D with AddComponent<> [OK]

Hint: Use AddComponent<CircleCollider2D>() for circle colliders [OK]

Common Mistakes:

• Using wrong collider type in AddComponent
• Missing angle brackets <> in AddComponent
• Confusing BoxCollider2D with CircleCollider2D

3. What will happen if you assign a PolygonCollider2D to a GameObject and set its points to form a triangle shape?

medium

A. The GameObject will have a circular collision area ignoring the points.

B. The GameObject will have a triangular collision area matching the points.

C. The GameObject will throw a runtime error due to invalid points.

D. The GameObject will have a box-shaped collision area by default.

Solution

1. Step 1: Understand PolygonCollider2D behavior

   PolygonCollider2D uses points to define a custom shape for collision.

2. Step 2: Setting points to triangle shape

   When points form a triangle, the collider matches that triangle shape exactly.

3. Final Answer:

   Triangular collision area matching points -> Option B

4. Quick Check:

   PolygonCollider2D shape = points defined [OK]

Hint: PolygonCollider2D matches shape from points given [OK]

Common Mistakes:

• Assuming PolygonCollider2D defaults to box or circle
• Expecting errors from valid point sets
• Confusing PolygonCollider2D with BoxCollider2D

4. You wrote this code to add a BoxCollider2D but it doesn't appear on your GameObject:

var collider = gameObject.AddComponent<BoxCollider2D>;
collider.size = new Vector2(2, 3);

What is the error?

medium

A. AddComponent cannot be used in scripts

B. BoxCollider2D does not have a size property

C. Vector2 should be Vector3 for size

D. Missing parentheses after AddComponent<BoxCollider2D>

Solution

1. Step 1: Check AddComponent syntax

   AddComponent is a method and requires parentheses: AddComponent<Type>()

2. Step 2: Identify the missing parentheses

   The code uses AddComponent<BoxCollider2D> without () which causes no component to be added.

3. Final Answer:

   Missing parentheses after AddComponent<BoxCollider2D> -> Option D

4. Quick Check:

   AddComponent needs () to work [OK]

Hint: Always add () after AddComponent<Type> [OK]

Common Mistakes:

• Forgetting parentheses after AddComponent
• Confusing size property with other collider types
• Using Vector3 instead of Vector2 for 2D colliders

5. You want to create a complex-shaped 2D character with both circular and polygonal parts. Which approach correctly combines colliders for best collision detection?

hard

A. Add multiple Collider2D components: CircleCollider2D for round parts and PolygonCollider2D for complex parts

B. Use only a single PolygonCollider2D for the entire character

C. Use only CircleCollider2D colliders and ignore polygon shapes

D. Add a BoxCollider2D and scale it to cover all parts

Solution

1. Step 1: Understand collider combination

   Unity allows multiple Collider2D components on one GameObject for complex shapes.

2. Step 2: Match collider types to shape parts

   Use CircleCollider2D for round parts and PolygonCollider2D for complex shapes to get accurate collisions.

3. Step 3: Avoid oversimplifying with one collider

   Single collider types may not fit all parts well, causing inaccurate collisions.

4. Final Answer:

   Add multiple Collider2D components: CircleCollider2D for round parts and PolygonCollider2D for complex parts -> Option A

5. Quick Check:

   Combine colliders for complex shapes [OK]

Hint: Use multiple colliders for mixed shapes [OK]

Common Mistakes:

• Trying to use one collider type for all shapes
• Ignoring collider overlap and physics impact
• Scaling box collider to fit complex shapes