All content in this course uses:

Add a particle explosion on player death and a UI Toolkit Restart button for a polished game-over flow.

Restart the game with a bang

In this tutorial, you’ll add a particle explosion that triggers when the player is destroyed, then use UI Toolkit to create a 

 button that reloads the scene — giving your game a clean and satisfying game-over flow.

Overview

To get started with your explosion effect, you’ll add a basic particle system using the Built-in Particle System, Unity's  visual effects tool. In this initial step, you’ll set up a simple burst of particles then in the following step, you’ll refine that burst to look like a massive explosion.

Rename the new GameObject “ExplosionEffect”.

 When you create a particle system, Unity also opens a 

view that lets you play, pause, and restart the effect to preview it live.

window, make the following changes in the 

— you only want the effect to emit particles once in a burst.

 — This is how long the system will emit particles.

 — This will make the particles a more appropriate size.

 You can hover your cursor over any property label in the 

window to view a tooltip that briefly explains what it does — this is useful when exploring new particle system settings.

You now have a short, contained burst of a few particles — this is a good base for your explosion.

Add a basic particle system

Now that you’ve got a basic particle system in place, you’ll enhance it by adjusting how the particles are emitted and how they spread. In this step, you’ll create a short burst of particles, change the emission shape from a cone to a sphere, and add randomness to make the explosion look more dynamic.

 A burst emits all the particles at once, instead of gradually over time — perfect for explosions.

2.  Change the shape of the particle spread:

 Small, randomized particles help make the explosion look more organic and less uniform.

After this step, your explosion will feel much more satisfying — a quick, randomized burst that’s ready to be initiated whenever the player is destroyed.

Edit Emission, Shape, and Randomization

Now that your explosion looks the way you want, you’ll turn it into a prefab — a reusable GameObject template. Prefabs are essential when you want to create and reuse the same GameObject multiple times in your game, like spawning an explosion every time the player is destroyed.

 GameObject is now an instance of a prefab.


After confirming the prefab was created, delete the 

window — you’ll spawn it from code later.

 When a GameObject is saved as a prefab, you can safely delete it from the scene. You’ll still be able to access and instantiate it during gameplay using scripts.

Make the explosion a prefab

Now that your explosion is a prefab, you’ll trigger it from code when the player is destroyed. You’ll use Unity’s 

 method to create a copy of the prefab at the 

GameObject’s position right before it disappears. To do this, you'll add a reference to the prefab in your script and assign it using the 

1.  Add a public reference to the ExplosionEffect prefab:

Near your other variable declarations, add the following line of code:

window so you can assign the prefab without needing to find it in code.

2.  Instantiate the ExplosionEffect prefab when the Player GameObject is destroyed:

 method, add the following line of code before the 

 GameObject’s rotation. However, since the particle system is in the shape of the sphere, its rotation actually doesn’t matter.


3. Assign the prefab in the Inspector window and test:

Enter Play mode to test your explosion. 


 If you forget this step, the explosion won’t appear — Unity can’t instantiate a prefab it doesn’t know about.

 GameObject is destroyed — giving instant visual feedback and making the collision event feel more complete.

Trigger the explosion from your script

After the player explodes, you’ll want to give them a clear, easy way to try again. In this step, you’ll add a 

 button to your existing UI document, position it near the center of the screen, and apply some basic styling to make it visible and clickable.

 element will appear centered and stretched across the screen in the 

 The name you assign here (RestartButton) is what your script will use to reference this element — make sure it's spelled correctly.

4.  Apply styling to position and format the button:

button still selected, use the foldout (triangle) to expand the 

Use the foldout (triangle) to expand the 

. This will position the top of the button 50% down the screen.

 section) as you like to make the button more readable.

 window to help preview the layout if elements appear off-screen.

Save your UI document and return to the Unity Editor. Your 

Add and style the Restart button

 button is now part of the UI, but it shouldn’t be visible until the 

GameObject explodes. In this step, you’ll reference the button in your script and hide it at the start of the game by changing its 

 script, add the following line of code with your other UI variables:

2.  Find the button using its name in Start():

 method, add the following line of code after retrieving 

Make sure the spelling matches exactly with what you set in the 

3.  Hide the button at the start of the game:

, add the following line of code after assigning 

 removes it from the layout completely — it won’t take up any space or be visible.

Save your script and test your game. The 

 button should now disappear when the game starts.

Hide the Restart button at start

 button is connected and hidden at the start, it's time to reveal it when the player is destroyed. You'll do this by updating its 

 inside the same method that handles collisions — right after playing the explosion effect.

1.  Show the button in OnCollisionEnter2D():

 method (just after the explosion is instantiated), add the following line of code:

 makes the button visible and allows it to occupy space in the UI layout. 

, a system used in UI Toolkit (and CSS) where elements are laid out in a flexible row or column — so 

 simply means "display this element using standard flexible layout behavior."

Save your script and enter Play mode in Unity. The 

 button will now appear with the explosion effect.

Show the Restart button on collision

 button appears on game over, it’s time to make it functional. In this step, you’ll write a method that reloads the current scene and hook it up to the button’s 

 so players can start fresh with a single click of the button.

 script, add the following method inside your class before the final closing curly brace (

 — a block of code that runs only when it’s called.

 means the function doesn’t return a value — it just performs an action. If that’s confusing, don’t worry — you’ll learn more about return types later. For now, just know that “void” is what you use when you’re not expecting any data output.

 is something you choose — you can name it anything, but clear names help others (and future you) understand what it does.

Inside the function, you're calling Unity's built-in scene load command, using the current scene’s name to reload it.



2.  Add the SceneManager library (if needed):

 is underlined or causes an error, add the following line of code to the top of your script:

Some IDEs (like Visual Studio or Rider) may add this automatically as you type the code. You can also hover over the red underline and use a suggested import to resolve it.


 method, so the scene reloads when the player selects the 

 symbol is the same one you used earlier to increment 

. Here, it means "add this method to the list of things that happen when the 

 button is selected." You're not adding numbers — you're adding functionality.

 button will reset the game and return everything to its initial state — completing the core game loop.

Reload scene on click

If you have any errors in your code or you just want to make sure your script matches exactly what has been taught up to this point, feel free to reference or copy the final code sample below. 

Final script sample

Try these optional activities to challenge yourself, build your skills, and improve your project.

 difficulty so that you know what to expect. You can complete one, all, or none of them — it’s totally up to you. If you’re not interested in doing these challenges, mark this step as complete and proceed to the next tutorial.

 view can get a little tedious. Try creating a custom 

 window and arrange it to take up one side of your screen in the Unity Editor.

 view visible somewhere on the other side.

When you're happy with the layout, go to the upper-right corner of the Editor, open the 

Expert: Add impact effects when obstacles collide

Make your game feel more reactive by spawning small bursts of particles every time obstacles bounce off walls. 

Create a small impact particle effect prefab (similar to your explosion but scaled down).

 to instantiate the small impact particle effect prefab at the collision point.

 to make bigger impacts for stronger impacts. To avoid spawning two particle effects for every collision, you could further optimize this by comparing the two colliding obstacles’ linear velocity and only spawning the particle effect for the faster-moving one. 

 to display the player’s best score ever.

When the game ends, compare the current score with the saved one.

Add a new UI Label to display the high score along with the current score.

You’ll likely need to do some online research and consult the 

 Want to challenge yourself? Use UI Toolkit animation to make the high score fade in or flash if it gets beaten.

Optional: More things to try

In this tutorial, you added an explosion effect and a 

 button to complete your game loop. In the next tutorial, you’ll have the chance to add some more optional features to your game.

Next steps

Control the execution of code with common logic structures 

Level 1 Application Scripting

Joy Horvath

Instructional Designer

Create user interfaces in an application and write code to implement defined functionality.

Programming User Interfaces

Write code to implement systems and structures for complex projects.

Level 2 Application scripting

Create simple particle systems to add dynamic environmental and gameplay effects to your scenes.

Beginner Particles and Visual Effects

ElizabethMidgley

GameObjects

lunaduranp

Gaming

Select the appropriate common Unity methods to use, e.g., Awake, Start, Update, FixedUpdate, Collision, and Trigger Events, given a desired feature to code

Achieve a desired result by using Unity API methods, given Unity’s script documentation

Achieve a desired result with different parameters by using various method overloads

Distinguish a correct use of any given Unity API method from an incorrect use

Control or trigger the state of components, such as an Animator Controller, Light, AudioSource, or User Interface element by using appropriate methods

Construct an input listener, given a scenario where a specific type of input is required

Print a message consisting of concatenated strings and variable values to the console by using Unity's Debug.Log method

Compose scripts that utilize various APIs

Configure UI components to be used with scripts. 

Arrange UI components on the canvas according to a defined layout using anchors, pivots, and groups. 

Organize UI components using optimization best practices such as using nested canvases. 

Configure UI components to be used with scripts.

Arrange UI components on the canvas according to a defined layout using anchors, pivots, and groups.

Organize UI components using optimization best practices such as using nested canvases.

Create user interfaces as defined in design documents.

Call the appropriate start-up methods in the initialization sequence of the app

Save user data in a the shutdown sequence of the app

Load the next scene when triggered by an event

Create the scene flow in an application state

Set up a new Particle System in the scene

Play, pause, stop, and restart a particle system in Scene view by using the Particle Effect window

Create a single burst of particles, rather than a continuous emission over time by using the Bursts section of the Emission module

Explain how individual Particle Systems can be combined to create more complex effects

Locate the Main module of a Particle System

Recall the three modules enabled by default in a Particle System: Emission, Shape, and Renderer

Configure a Particle System's main properties, such as lifetime, size, and max particles by modifying the Main module

Control the location and initial direction of particles by modifying the Shape module

Control the rate and timing of particles by modifying the Emission module

Control the appearance of individual particles by modifying the Renderer module

Add randomness to a Particle System by using the Random Between Two Constants feature

Change the color of a particle over its lifetime by using the gradient editor and the Color Over Lifetime module

Change the size of a particle over its lifetime by using the curve editor in the Size Over Lifetime module

Unity Version 6.3