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Build a physics-based player ship that follows mouse input, applies thrust, and reacts to collisions using Unity’s input and physics systems.

Steer the player

In this tutorial, you’ll create a controllable player ship that turns to face your cursor and moves in that direction when you click the left mouse button. Along the way, you’ll learn how to detect input, convert mouse cursor position into world space, apply directional thrust, and respond to collisions — all using Unity’s physics and input systems.

Overview

Before you can control the player, you need something to control. In this step, you’ll create a triangle-shaped 

GameObject, made up of multiple simple 2D shapes. This GameObject will represent the player’s ship and point in the direction it moves.

 value will move it down on the screen, giving the player a bit more room in front from their starting position.


2.  Add a triangle sprite as the main shape:

The problem with using a simple triangle like the default 2D sprite GameObject is that it would not be able to convey which direction the ship is facing. You need to add more shapes to make that more clear. 

In the Hierarchy window, right-click the 

 GameObject again and add another 2D sprite (like a square, capsule, or another triangle).

Move, rotate, and scale the additional shape using the 

Adding another shape helps visually indicate the ship's forward direction, which will become important when you apply thrust.


 GameObject looks like a small ship, and the pointer clearly shows which way it's facing.

 You can also scale the entire multi-part ship up or down by adjusting the 

5. (Optional) Edit the Player’s sprite colors

 GameObject’s child GameObjects, select the 

You now have a visible player ship made from grouped sprites that’s ready for physics and input control in the next steps.

Set up the Player GameObject

Now that your player ship is built, it needs physical properties so it can move and collide with other GameObjects. In this step, you’ll add a 

 GameObject  to interact with the physics system.

Because your ship is made of multiple parts, you’ll use 

 — separate colliders attached to each child GameObject. Unity treats the combined colliders as one when physics is applied to the parent.

1.  Add a Rigidbody 2D component to the Player GameObject:

2.  Add colliders to all child GameObjects:

) and select all the child GameObjects of the 

 (or any other collider shape that fits).

component is a flexible option that fits most sprite shapes closely.


The player won’t move yet, but it should now respond to physics — See what happens when one of the flying obstacles collides with the 

You’ve now given your player a physical presence in the world, using 

 components. Next, you’ll start scripting input so the ship can detect mouse clicks and respond.

Add required physics components

In this step, you’ll create a new C# script called 

 GameObject. This script will handle all of the player’s input, movement, and collision logic.

This script is a custom component — a set of instructions you write that Unity will run during the game.

 Make sure the filename is spelled correctly when you rename the script (

). Unity requires that the script name exactly matches the class name inside it. If the names don’t match, you’ll get an error. If you make a mistake on its spelling, delete the script and create it again with the correct name.

2.  Attach the script to the Player GameObject:

You’ll edit this script over the next several steps to handle input and movement.

Create the PlayerController script

In this step, you’ll write your first input detection code — specifically when the mouse is clicked. To do that, you’ll use the 

 statement (like importing a library) at the top of your script.

, and it runs once per frame — making it ideal for checking input, which can change at any time.

 window to print a message every time the mouse is clicked so you can test that the mouse clicks are being detected correctly.

2.  Add code to detect clicks inside Update():

Then, add the following lines of code inside the braces (

This checks if the left mouse button is currently being pressed down.

3.  If you see an error under “Mouse”:

You might get a red underline or error in the 

To fix this error, add the following line of code at the very top of your script:

 If you’re using a modern code editor like Visual Studio or VS Code, you might be able to hover over the error and select a 

 to automatically add this line. If you don’t see an error under “Mouse”, it likely means your editor already added the correct 

 directive automatically for you as you were typing.

 window by selecting the Debug message that appears underneath the 

Look for the message: "Mouse was pressed"



You’ve now detected real-time input using Unity’s Input System. Next we have to actually do something with that input. 

Detect mouse clicks

Now that your script can detect mouse clicks, it’s time to figure out where the mouse is clicking. In this step, you’ll log the 

By default, Unity detects mouse position as a 

(X, Y, and Z coordinate), but it does so in 

 — a coordinate system based on pixels where (

) starts at the lower-left corner of the screen.

) is usually in the center of the scene. You’ll learn how to log the screen-space position now — and convert it to world space in the following step.

1.  Update your if block to store the mouse position:

 code, add the following line of code to declare a new 

 is a structure that stores 3 values (X, Y, Z). Mouse position is given as a Vector3, even in 2D games.

 coordinates — based on the resolution of the 

2.  Log the mouse position to the Console message:

 code to now display the mouse position, in addition to the fact that the mouse was pressed:

) to save your script, then return to Unity and enter

Notice how the numbers increase as you move the mouse to the right (X) and up (Y). This is different from Unity’s world space, which centers around (

Log the mouse position

, so you need to convert those coordinates. In this step, you’ll use Unity’s 

 function to translate the mouse’s position from screen space to a point in the game world.

This is one of the most important transformations in Unity when dealing with player input.

1.   Replace the old mouse position line with a world-space version:

 takes screen coordinates (from the mouse) and converts them to world coordinates that match your scene layout.


) to save, then return to Unity and enter

window. When you click the center of the screen, you’ll now see values centered closer to (

, and you might notice the Z position might be at an unexpected value — that’s okay in 2D! Since your game takes place in the X-Y plane, Z doesn’t affect gameplay here.

You’ve now successfully converted input from screen space to world space — which means your 

 GameObject can begin responding to mouse position in a meaningful way.

Convert mouse position to world space

Now that you know the position of the mouse in world space, you can rotate the player to face that position. You’ll do that by calculating the 

GameObject’s position and the mouse position, then setting the 

 controls which way a GameObject is facing in 2D — it’s the local Y-axis direction. When you set 

, you’re telling Unity to rotate the GameObject so that its upward axis points toward that direction vector.

1.  Calculate the direction to the mouse:

 block (after getting the mouse position in world space), add the following line of code:


This line subtracts two positions: the mouse's position minus the 

2.  Set the Player GameObject’s facing direction:

Add the following line of code underneath the previous one:

This tells Unity to rotate the player so that its “up” direction now points along the direction vector.

This is an easy way to rotate a GameObject without using angles or complex math.


) to save, then return to Unity and enter Play mode.

GameObject will now visually rotate to point toward the mouse.


 to align the player’s rotation with a direction — a fast and effective way to handle orientation in 2D games.

Rotate the Player GameObject to face the mouse

GameObject rotates to face the mouse, it’s time to make it move. In this step, you’ll apply force in the direction of the mouse click using Unity’s physics system.

Rather than hardcoding the strength, you’ll create a 

 so you can adjust the thrust directly in the 

window later — a good coding habit for tuning gameplay.

1.  Add variables at the top of your script:

2.  Get the Rigidbody 2D component in Start():

 method, add the following line of code to assign the 

3.  Apply thrust inside the if-statement block:

 is the vector pointing toward the mouse.

 controls how strongly the force is applied.


GameObject should rotate and move toward the mouse when clicked.

GameObject becomes hard to control and goes too fast — don’t worry! You’ll fix that in a future step.

Apply thrust in mouse direction

GameObject’s speed depends on how far you click from the ship. That’s because longer direction vectors apply more force. In this step, you’ll fix that by 

 the direction vector — a technique that keeps the direction the same but limits its length to 

GameObject will always move at a consistent speed, no matter where you click.

1.   Update the direction line to normalize the vector:

Surround the subtraction calculation in parentheses and normalize the value:

 that resizes the vector to a length of 1 (but keeps its direction).

Click near the ship, then far away — your 

GameObject will now move at the same speed no matter where you click.


Try increasing or decreasing the value until the controls feel intuitive.

Changes you make during Play mode will not be saved. You can experiment in Play mode, then set the value you want after exiting Play mode. 

Normalize the direction variable

GameObject moves around the world, it needs to respond to collisions. In this step, you’ll add a method called 

 that gets triggered automatically when a collision happens.

GameObject from the scene when it hits another GameObject with a collider — either an obstacle or an outer wall — simulating a game-over effect.

 script before the final closing curly brace (outside of 

 If autocomplete in your code editor is working, try entering “

 from the suggestion list. This ensures you get the spelling and function formatting correct. If your autocomplete isn’t working, you can just copy and paste the code above. 

Unity calls this method automatically when a 2D collider hits another 2D collider, but only if one of them has a 

) to save, then go back to Unity and enter Play mode.

GameObject— when you hit a wall or obstacle, the 

Handle collisions

Before you move on, it’s a good habit to clean up your script. In this step, you’ll remove old 

 statements that you used for testing and add a few code comments to make your script easier to read.

 are a core part of writing clean code — they help explain what your code does without affecting how it runs. This is especially helpful when you come back to your project later or share your work with others.

 calls. Now that you know everything is working as expected, they’re not needed any more and will clutter the 

2.  Add helpful comments throughout your script:

) to add short notes above important lines of code.

The following examples are good to include:

Make sure the Unity Editor updates and there are no errors in the 

Clean up your code

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. 

Medium: Clamp the Player GameObject’s max speed

If you hold the mouse for a while, your ship can accelerate endlessly. You can clamp the maximum speed to prevent it from becoming uncontrollable.

With this code, the ship can still accelerate, but it won’t go faster than your defined top speed — making movement feel tighter and more intentional.

Add a little visual flair when the ship is accelerating — just like a jet engine firing.

GameObject and create a new triangle sprite as a child GameObject, then rename it “BoosterFlame”.

Scale and rotate the sprite so it appears behind the ship.

window by disabling the checkbox next to its name so that the flame is hidden by default.


Optional: More things to try

You’ve created a controllable player ship that rotates toward the mouse, applies thrust when clicked, and responds to collisions. In the next tutorial, you’ll build a scoring system that tracks how long the player survives and displays that score on screen in real time.

Next steps

Identify the defaults elements in a new scene, Create and manipulate GameObjects and configure their components.

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Explain the Toolbar buttons used to manipulate objects.

Select a GameObject from both the Hierarchy window and the Scene view.

Link GameObjects in parent-child relationships using the Hierarchy window to create complex GameObjects.

Explain the relationship between the Scene view and the Inspector window.

Move, scale, and rotate a GameObject using the Toolbar buttons and the mouse in the Scene view.

Move, scale, and rotate a GameObject using the Transform Component in the Inspector window.

Position Sprites in 3D space in a 2D Scene.

Use 3D GameObjects in a 2D Scene to group Sprites.

3.1 Explain the Toolbar buttons used to manipulate objects.

3.2 Select a GameObject from both the Hierarchy window and the Scene view.

3.3 Link GameObjects in parent-child relationships using the Hierarchy window to create complex GameObjects.

3.4 Explain the relationship between the Scene view and the Inspector window.

3.5 Duplicate a GameObject.

3.6 Move, scale, and rotate a GameObject using the Toolbar buttons and the mouse in the Scene view.

3.7 Move, scale, and rotate a GameObject using the Transform Component in the Inspector window.

3.8 Position Sprites in 3D space in a 2D Scene.

3.9 Use 3D GameObjects in a 2D Scene to group Sprites.

Transform GameObjects

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

Reduce redundancy and improve code's readability by correctly naming variables and methods

Describe common naming conventions including PascalCase and camelCase

Cultivate a code style that is efficient and easy to read

 Implement basic physics for GameObjects 

Apply RigidBody or RigidBody 2D components in order to enable GameObjects to act under the control of physics

Modify the basic properties of a RigidBody or RigidBody 2D component in order to control how the GameObject is affected by physics, including its mass, its drag, and the Scene's gravity

Unity Version 6.3