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Learn to adapt your code to create static damage zones that reduce player health and grant brief invincibility.

Add damage zones to decrease health (static hazards)

In this tutorial you’ll create static damage zones to decrease the player character’s health.

By the end of this tutorial, you’ll be able to do the following:

Adapt your previous code to decrease player character’s health.

Implement a period of invincibility when the player character's health is decreased.

In your game, the player can increase their 

’s health up to the maximum level, but there’s currently nothing that can negatively impact that health. In this tutorial, you’ll apply what you’ve previously learned to decrease the 

's health when they enter a damage zone (collide with a particular GameObject). Later in the course, you’ll build on this work to create moving enemies too.

: For the purposes of this tutorial, we chose to use the 

 asset set, and the images used in instructions will reflect this. If you chose another asset set, the file names will be the same, but in your corresponding theme folder.

Overview

When you set up the health collectibles, you set the 

 at game launch. To update your script so the 

 GameObject starts the game with full health, follow these instructions:

 At the top of the script, find the variable declaration for 

, and update the declaration so it no longer sets the variable to 

 function, remove the double slashes from the instruction to set 

 function will now execute this instruction when it runs.

Adjust the currentHealth value at game start

Throughout this course, you’ll find a few challenges where you’re encouraged to try writing the code on your own. But don’t worry – if you want to make sure you did it correctly, you can review the script later in the step.

’s health on collision – now you’ll do the opposite and decrease the 

Apply what you’ve learned so far to set up a functioning

 prefab. The damage zone should decrease the player character’s health value by one when the character collides with it.

The damage zone for the Ruby asset pack positioned in multiple locations in the Scene view, with its GameObject also visible in the Hierarchy. 

Check your DamageZone GameObject configuration

Review these high-level instructions to confirm that you’ve set up the damage zone correctly:

 In prefab editing mode, make sure you’ve added a 

property automatically updates the size of the collider to fit the area of the GameObject.

 Create a new script called “DamageZone” and attach it to the 

 script code and adapt it to decrease the player character’s health instead of increasing it:

The only condition for the health to decrease is whether the colliding GameObject has a 

Damage zones that disappear immediately wouldn’t be very powerful, so the instruction to destroy the GameObject after collision has been removed.

 Save your changes and return to the Unity Editor. Test the damage zone to confirm that it decreases the player character’s health on collision.

Challenge: Create a functioning damage zone

At the moment, the player character’s health decreases by one when they enter the damage zone (hit its collider), but that’s the only damage the zone does. That approach isn’t very challenging for players – the zone should cause ongoing damage for as long as the player character is within its collider.

To adjust the damage zone functionality, follow these instructions:

 is called every frame that the GameObject with the 

 component is inside the collider, not just when it enters. This change means that the damage zone won’t have a one-time impact – the function will continue to be called as long as the player character is in the damage zone.

 Save your changes, return to the Unity Editor, and test the updated functionality.

You should notice that when the player character enters the 

 gets to zero in less than a second (in five frames, to be precise, unless you have adjusted the 

: Remember to exit Play mode when you’ve finished testing.

 Inspector window showing a Rigidbody 2D component. The Sleeping Mode property is highlighted and set to “Never Sleep”

By default, the physics system stops computing collisions for a GameObject with a 

 component when that GameObject stops moving: the 

. This approach optimizes resources and avoids wasted calculations. However, for the damage zone to work properly, you need that computation to happen even when the 

Refine your damage zone functionality

Your adjustment to make the damage zone more dangerous also means that the player character loses all their health almost immediately. Even if you want to make your game challenging, the current configuration is impossible for a player to overcome.

There are different ways that you can address this issue. In this case, you’ll make the player character invincible after they receive damage for a brief cooldown period to avoid complete loss of health immediately.

To add a damage cooldown period after the player character takes damage, follow these instructions:

 class, with the other variable declarations, add the following lines of code:

 controls how long the player character remains invincible after taking damage, measured in seconds. This variable is public, so you can adjust it in the 

 stores whether the player character is currently invincible.

 stores how much time is remaining until the player character is no longer invincible and can take more damage.

 statement that will execute if the player character’s health is currently being decreased:

parameter having a value below zero. The value will be below zero if a health decrease has been made through the 

 function if the player character is already invincible using the 

 statement to end a function early if a particular condition is met.

 to avoid further damage during the cooldown period.

 (the cooldown timer) to the current value for the public 

 statement that will be executed if the player character is currently invincible:

 statement and code block are enclosed within the closing brace of the 

 – that is, the player character has taken damage since the last time that 

The first instruction in the block subtracts (-=) 

is the interval in seconds from the previous frame to the current one, so the instruction reduces the 

 statement follows, with the condition that any instructions in the block after the 

 is less than zero – that is, when the timer countdown has finished.

, meaning that the player character is once again vulnerable to damage after the countdown finishes.

Save your changes and return to Unity Editor.

Implement a cooldown after the character takes damage

Now that you’ve written the cooldown functionality, test it and adjust the cooldown duration:

 Enter Play mode and test that the damage cooldown functionality works.

’s health at two second intervals while the 

 is within the damage zone collider – you can find the notifications of this in the 

Unity Console screenshot showing three log entries with timestamps and progress fractions: [23:03:44] 4/5, [23:03:46] 3/5, [23:03:48] 2/5, each labeled “UnityEngine.Debug:Log (object).

 value and test the player experience until you are happy with the damage cooldown time.

Exit Play mode and save your changes when you’ve finished testing.

: You can always adjust the cooldown again later as you continue to develop your game. You might also find it helpful to get specific user feedback on the damage cooldown period when you’ve created the full 

Test your changes and adjust the TimeInvincible value

If you want to further develop your skills, explore new concepts, or improve your project, check out some of the optional activities below. Each one is tagged as either Easy, Medium, or Difficult, so you can choose the level of challenge.

These activities are entirely optional, so if you’re not interested, no problem – just skip this step. We do recommend attempting at least one of them in order to get the most out of this learning experience. Good luck!

Easy: Position damage zones to challenge the player

Take some time to experiment with your placement of damage zones and health collectibles within the environment, and consider the fact that you’ll soon add moving enemies too. It’s important to give your players sufficient challenge, but that needs to be balanced – an almost-impossible game probably isn’t your goal here!

In the previous tutorial, we mentioned you could create health collectible variants that increased the 

’s health by different values. You can take a similar approach here by creating prefab variants of the 

If you want to practice applying what you’ve learned in this unit, you can configure slow healing zones that increase the 

’s health using the same principle as the damage zones. You know everything that you need to implement this functionality.

More things to try (optional step)

Take a moment to check that your scripts are correct before continuing.

: If you completed any extension work in your script, this will not be reflected in the reference script below.

Check your scripts

The player character has a fully-functional health system, and can both take and heal damage. However, at the moment, the player has no way of knowing what their health level is – you’ve been using the 

 window as you test, but that won’t help your player. In the next unit, you’ll create a heads-up display (HUD) and configure it to show the player character’s health level.

Unity Version 6.3