Introduction

This tutorial covers how to add an Enemy to your project. To speed up the process we'll be importing an existing entity rather than building a new one ourselves. Once imported, we will modify the entity so it has the functionality we'll need for this tutorial - specifically adding the ability for the enemy to take damage.

Importing Enemy Entity

To import the entity

1. Download the exported entity file from here: https://github.com/vchelaru/FlatRedBall/raw/NetStandard/Samples/Platformer/DealingDamage/Enemy.entz

2. In Glue, right-click on the Entities folder

3. Select Import Entity
4. Navigate to the location where you saved the Enemy file earlier and click OK

We now have a fully-functional enemy which has:

• Collision shape named AxisAlignedRectangle

• Sprite displaying a walking animation

• Platformer values so that it can collide with solid collision

• EnemyInput object which will keep the enemy from moving (does not use the gamepad or keyboard)

Adding EnemyList to GameScreen

We will add a list to our GameScreen and an instance of our Enemy to Level1 so we can see the enemy in game. To add an enemy list to GameScreen:

1. Select the Enemy entity

2. Select the Quick Actions tab

3. Click the Add Enemy List to GameScreen button - this creates a list of enemies which we'll use to create collision relationships later

4. Click the Add Enemy Factory button - this allows us to create enemies in code and Tiled maps.

To add an enemy to your Level1:

1. Drag+drop the Enemy entity onto Level1\
2. Select Enemy1 and click on the Variables tab

3. Set X to 160

4. Set Y to -160

Now we have an enemy in the game, but it falls through the level. We can fix this by telling the enemies to collide against our GameScreen's SolidCollision object:

1. Expand GameScreen

2. Expand the Objects folder

3. Drag+drop the EnemyList onto the SolidCollision object

If we run the game now, the enemy will fall and land in the level next to the player.

Introduction

We’ll begin this tutorial with an empty project. Mine will be called EnemyDamage.

Glue Wizard

The Glue Wizard can help us get a quick project set up. We will leave most of the options to their default, but we will change the following:

Player Entity

• Change What kind of control will the player have? to Platformer

• Uncheck Add Sprite to Player Entity unless you intend to add graphics to your Player entity. This tutorial will not cover how to add graphics to the Player entity.

Note that we will not be explicitly working with the Player entity in this game, but we still create one since most games need one eventually.

Levels

• Change Number of levels to create to 1. We will only have one level in this game

Conclusion

Now our project is ready to go as a fully functional platformer. We can begin adding the Enemy entity in the next tutorial.

This set of tutorials covers how to create enemies which can receive damage from Bullets created by the Player. Many games include enemies which can take damage from the player such as Mega Man X and Super Metroid.

The following pages cover a number of topics related to dealing damage:

• Dynamic entity creation and destruction (Bullets)

• HP and damage amounts

• Damage over time and area of effect

• Friendly fire and teams

Introduction

This tutorial adds a Bullet entity which the player can shoot. The Bullet entity has the following characteristics:

• It will be visually represented by a circle

• It moves left or right depending on which way the Player is facing when shooting

• It will be destroyed when colliding with the SolidCollision

• It will be destroyed when colliding with the Enemy

Creating Bullet Entity

To create a Bullet:

1. Click the Quick Actions tab

2. Click the Add Entity button
3. Enter the name Bullet

4. Click the Circle checkbox under Collisions

5. Leave all of the rest of the values default and click OK

When a Bullet is created, it will move either left or right. We need to control the speed of the bullet. We will create a variable which we'll use in our code later:

1. Select the Bullet entity

2. Click on the Variables tab

3. Click the Add New Variable button
4. Verify that float type is selected

5. Enter the name BulletSpeed

6. Click OK
7. Enter a value of 300 for BulletSpeed

We will also want to change the radius of the Bullet's CircleInstance:

1. Expand the Bullet Objects folder

2. Select CircleInstance

3. Click the Variables tab

4. Change Radius to 6

Creating a Bullet in Player

The Bullet creation logic will be added to the Player entity. We need to detect if the shoot button has been pressed. If so, we'll create a new bullet and have it move in the direction that the player is facing. To do this, open Player.cs in Visual Studio and modify the code as shown in the following snippet:

IPressableInput

CustomInitializePlatformerInput

Whenever the input device is set on a platformer entity, the CustomInitializePlatformerInput method is called. Since our entity has custom input for shooting, we add the CustomInitializePlatformerInput where we assign shootingInput according to our InputDevice type. In this case we assign shooting to the right ALT key if using a keyboard and the X button if using an Xbox360GamePad. Any re-assignment of input should be done in CustomInitializePlatformerInput rather than CustomInitialize. This is because the order in which code is executed. When considering input, assignment, the following is performed:

1. CustomInitialize

2. InputDevice is assigned (can be assigned in generated code or custom code)

3. CustomInitializePlatformerInput which is called whenever the input device is assigned.

CustomInitialize always runs before an InputDevice is assigned. We want our shootingInput-assigning code to run after the InputDevice is assigned, so we should put it in CustomInitializePlatformerInput.

shootingInput.WasJustPressed

Finally, we check our shootingInput.WasJustPressed to see if the user just pushed the input. If so, we create a bullet and set its XVelocity according to the direction that the Player is facing. If we run our game now, we can shoot bullets in the direction we're facing.

Destroying Bullets

Currently, our bullets can move through walls and enemies. First we'll add collision between our GameScreen BulletList and SolidCollision:

1. Expand the GameScreen Objects folder

2. Drag BulletList onto SolidCollision to create a new collision relationship
3. Select the new BulletListVsSolidCollision relationship

4. Click the Collision tab

5. Click the Add Event button
6. Click OK to accept the defaults

Now we can destroy the bullet whenever the event occurs:

1. Open the project in Visual Studio

2. Go to GameScreen.Event.cs

3. Find the BulletListVsSolidCollisionCollisionOccurred method

4. Modify the code as shown in the following snippet:

Now we can shoot bullets and they will get destroyed when they hit the wall.

Conclusion

We end this tutorial with the ability to shoot bullets and destroy them when they hit the wall. The next tutorial will implement the ability to damage and destroy enemies.

Introduction

This tutorial will implement dealing damage to an Enemy. Rather than immediately destroying the Enemy when it collides with a Bullet, we'll implement health points (HP) which can be reduced when an Enemy collides with a Bullet. Once an Enemy's HP is reduced to 0, it will be destroyed.

Adding Enemy HP

Typically enemies will have two values for HP:

• MaxHP - the starting number of HP when an Enemy is first spawned

• CurrentHP - the number of HP that the enemy currently has

The MaxHP is a designer variable - a variable which a game designer may change during the development of the game to adjust difficulty. We'll define this in Glue so it can be changed easily. By contrast, CurrentHP is a logic variable - a variable which is used in game logic and which should not be modified by a game designer. It will initially be assigned to MaxHP and will be reduced whenever the Player takes damage. To define a MaxHP variable:

1. Select the Enemy entity

2. Click on the Variables tab

3. Click the Add New Variable button
4. Select the int type

5. Enter the name MaxHP

6. Click OK
7. Set the new MaxHP variable to 6

Now we can add the CurrentHP value to the Enemy:

1. Open the project in Visual Studio

2. Open Enemy.cs

3. Add the CurrentHp variable and modify CustomInitialize as shown in the following code snippet

In a typical game, whenever an Enemy takes damage the game may perform many actions such as:

• Flashing the Enemy or playing some visual effect

• Playing a sound effect

• Showing the amount of damage dealt (as a floating number)

• Modifying how much health is shown in a health bar

• Destroying the Enemy and showing a death effect if the Enemy has died

Keeping this logic in the Enemy.cs file can help keep code organized, so we'll be adding the following function to the Enemy.cs file:

Be sure to make the TakeDamage method public so it can be called from outside of the Enemy class.

Bullet vs Enemy Collision

Now we can create a collision relationship between the BulletList and EnemyList objects in the GameScreen:

1. Expand the GameScreen Objects folder

2. Drag+drop the BulletList object onto EnemyList\
3. Select the new BulletListVsEnemyList relationship

4. Click on the Collision tab

5. Click the Add Event button
6. Accept the defaults and click OK

Now we can fill in the event method. Open GameScreen.Event.cs and modify the BulletListVsEnemyListCollisionOccurred method as shown in the following snippet:

Now we can shoot at the enemy. After six shots, the enemy is destroyed.

Conclusion

Now we've created a game where we can destroy an enemy with 6 shots. A real game would have more than one enemy, but if we add additional enemies, our game will automatically collide bullets against each enemy, and each enemy will keep track of its own HP.