Enemy patrol and chase patterns in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the enemy move between two points.

Unity

Vector3 targetPosition = points[[1]].position;
transform.position = Vector3.MoveTowards(transform.position, targetPosition, speed * Time.deltaTime);

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

A2

B1

C0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using an index out of range like 2 or 3 causes errors.

Starting at index 1 skips the first point.

The enemy starts moving towards the first point, which is at index 0 in the points array.

2fill in blank

medium

Complete the code to check if the enemy reached the patrol point.

Unity

if (Vector3.Distance(transform.position, points[currentPoint].position) [1] 0.1f) {
    currentPoint = (currentPoint + 1) % points.Length;
}

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

A<

B>

C>=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of < causes the condition to never be true.

Using >= or <= changes the logic incorrectly.

The enemy is considered to have reached the point if the distance is less than 0.1 units.

3fill in blank

hard

Fix the error in the chase code to make the enemy follow the player.

Unity

transform.position = Vector3.MoveTowards(transform.position, [1], speed * Time.deltaTime);

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

Aplayer

BplayerPosition

Cplayer.transform

Dplayer.transform.position

Attempts:

3 left

💡 Hint

Common Mistakes

Using player or player.transform directly causes type errors.

Using playerPosition if not defined causes errors.

The MoveTowards method needs a Vector3 position, so we use player.transform.position.

4fill in blank

hard

Fill both blanks to make the enemy switch from patrol to chase when close to the player.

Unity

if (Vector3.Distance(transform.position, player.transform.position) [1] chaseRange) {
    isChasing = [2];
}

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

A<=

Btrue

C>

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of <= reverses the logic.

Setting isChasing to false stops chasing.

The enemy starts chasing when the player is within chaseRange, so distance <= chaseRange and isChasing is set to true.

5fill in blank

hard

Fill all three blanks to make the enemy stop chasing and resume patrol when the player is far.

Unity

if (Vector3.Distance(transform.position, player.transform.position) [1] chaseRange) {
    isChasing = [2];
    currentPoint = [3];
}

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

A>

Bfalse

C0

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > reverses the logic.

Setting isChasing to true keeps chasing.

Not resetting currentPoint causes patrol to start at wrong point.

The enemy stops chasing when the player is farther than chaseRange, so distance > chaseRange, isChasing is false, and patrol restarts at point 0.

Practice

1. What is the main purpose of an enemy patrol pattern in Unity game development?

easy

A. To make the enemy jump randomly

B. To move the enemy between set points repeatedly

C. To make the enemy disappear and reappear

D. To make the enemy shoot projectiles continuously

Solution

1. Step 1: Understand enemy patrol behavior

   Enemy patrol means moving the enemy between fixed points in a loop to simulate guarding or searching.

2. Step 2: Identify correct behavior from options

   Only moving between set points repeatedly matches patrol behavior.

3. Final Answer:

   To move the enemy between set points repeatedly -> Option B

4. Quick Check:

   Enemy patrol = moving between points [OK]

Hint: Patrol means looping between points, not random actions [OK]

Common Mistakes:

• Confusing patrol with attack or random movement
• Thinking patrol involves shooting or disappearing

2. Which of the following is the correct way to check the distance between the enemy and player in Unity C#?

easy

A. float dist = enemy.position.Distance(player.position);

B. float dist = enemy.position - player.position;

C. float dist = Vector3.Distance(enemy, player);

D. float dist = Vector3.Distance(enemy.position, player.position);

Solution

1. Step 1: Recall Vector3.Distance syntax

   The correct method to get distance between two Vector3 points is Vector3.Distance(point1, point2).

2. Step 2: Check each option

   float dist = Vector3.Distance(enemy.position, player.position); uses Vector3.Distance with positions, which is correct. Others have syntax errors or wrong usage.

3. Final Answer:

   float dist = Vector3.Distance(enemy.position, player.position); -> Option D

4. Quick Check:

   Use Vector3.Distance(point1, point2) for distance [OK]

Hint: Use Vector3.Distance with positions, not subtract vectors directly [OK]

Common Mistakes:

• Subtracting vectors without calling Distance method
• Calling Distance on a Vector3 instance incorrectly
• Passing transforms instead of positions

3. Given this code snippet for enemy chase, what will be the output if the player is 3 units away and chaseDistance is 5?

if (Vector3.Distance(transform.position, player.position) < chaseDistance) {
    Debug.Log("Chasing player");
} else {
    Debug.Log("Patrolling");
}

medium

A. No output

B. Patrolling

C. Chasing player

D. Error at runtime

Solution

1. Step 1: Calculate distance and compare

   Distance is 3, chaseDistance is 5, so 3 < 5 is true.

2. Step 2: Determine which branch runs

   Since condition is true, "Chasing player" is printed.

3. Final Answer:

   Chasing player -> Option C

4. Quick Check:

   Distance 3 < 5 triggers chase [OK]

Hint: Compare distance to chaseDistance to decide behavior [OK]

Common Mistakes:

• Confusing less than with greater than
• Assuming no output if condition true
• Thinking code causes error

4. Identify the error in this patrol code snippet:

void Patrol() {
    int currentPoint = 0;
    transform.position = Vector3.MoveTowards(transform.position, patrolPoints[currentPoint].position, speed * Time.deltaTime);
    if (transform.position == patrolPoints[currentPoint].position) {
        currentPoint++;
        if (currentPoint >= patrolPoints.Length) {
            currentPoint = 0;
        }
    }
}

medium

A. currentPoint should be declared outside the method to keep its value

B. Vector3.MoveTowards is used incorrectly

C. Time.deltaTime should not be multiplied by speed

D. The if condition should use < instead of >

Solution

1. Step 1: Check variable scope for currentPoint

   currentPoint is reset to 0 every time Patrol() runs, so it never increments properly.

2. Step 2: Understand how to fix the scope issue

   Declaring currentPoint outside the method (as a class variable) preserves its value between calls.

3. Final Answer:

   currentPoint should be declared outside the method to keep its value -> Option A

4. Quick Check:

   Keep patrol index outside method to track progress [OK]

Hint: Keep patrol index as a class variable, not local [OK]

Common Mistakes:

• Thinking MoveTowards usage is wrong
• Confusing comparison operators in if
• Misunderstanding Time.deltaTime usage

5. How can you combine patrol and chase behaviors so the enemy patrols until the player is within 4 units, then chases the player, and returns to patrol if the player moves away?

hard

A. Use a state variable to switch between patrol and chase based on distance checks

B. Call Patrol() and Chase() methods simultaneously every frame

C. Only use Chase() method and ignore patrol points

D. Use a timer to switch behaviors every 5 seconds regardless of player position

Solution

1. Step 1: Understand behavior switching logic

   The enemy needs to switch between patrol and chase based on player distance dynamically.

2. Step 2: Use a state variable to track current behavior

   A state variable (like enum or bool) can control which method runs each frame depending on distance.

3. Step 3: Implement distance check to update state

   If player is closer than 4 units, set state to chase; else set to patrol.

4. Final Answer:

   Use a state variable to switch between patrol and chase based on distance checks -> Option A

5. Quick Check:

   State variable + distance check = behavior switch [OK]

Hint: Switch states based on distance, don't run both behaviors together [OK]

Common Mistakes:

• Running patrol and chase at the same time causing conflicts
• Ignoring player distance for switching
• Using timers instead of distance checks