Unity 2D Space Shooter Game

In today's Tutorial we will learn how to make a 2D Space Shooter Game in Unity with less than 100 Lines of Code. As usual everything will be explained as easy as possible so everyone can understand it.

Foreword

Our 2D Space Shooter will be inspired by the old arcade games that everyone loved when growing up.

We will make use of all kinds of different Unity features like Physics (including Rigidbodies and Colliders), Animations (Mecanim), Scripting (C#), Prefabs, Shaders and the Sprite Editor. The game art will be very easy to create with our drawing tool of choice.

Requirements

Knowledge

We will explain every single step in detail, but it's still a good idea to get a basic overview of Unity if you never used it before. Feel free to read through our easier Unity Tutorials like Unity 2D Pong Game to see what Unity is all about.

If you used Unity before then we can get started right away.

Unity Version

Our Space Shooter will use Unity 5.0.1f1. Newer versions should work fine as well, older versions may or may not work. The free version of Unity 5 now comes with all the engine features, which makes it the recommended version.

Creating the Project

Let's get to it. We will start Unity and select New Project:

We will name it spaceshooter, select any location like C:\, select 2D and click Create Project:

Making the World Black

At first we will select the Main Camera in the Hierarchy and then take a look over to the Inspector. We will change the Background color to black and adjust the size to 10:

Creating the Background

The Space Texture

Our background should consist of an image of stars that scrolls downwards so it appears as if the player is flying through space. We will begin by drawing a 256 x 512 px space background in our drawing tool of choice:

Note: right click on the image, select Save As..., navigate to the project's Assets folder and save it in a new Sprites folder.

Once saved into our Project, we can select the background image in the Project Area:

Afterwards we can modify the Import Settings in the Inspector:

Note: usually we would set the Texture Type to Sprite for a 2D game. But scrolling a texture with UV Mapping only works for Textures, not for Sprites. Sprites would be pixel perfect, but scrolling them requires a Shader that would be far too complicated for this tutorial.

Adding it to a Quad

Alright, let's add the background to our game. We will select GameObject->3D Object->Quad from the Top Menu in order to add a Quad to our game:

Note: we use a Quad from the 3D Object menu in a 2D game because a Texture (instead of a Sprite) can be added to it.

Now we will take a look at the Inspector and scale the quad so it has the same aspect ratio as our background texture:

We will also rename it to Background:

And remove the Mesh Collider because we won't need it (it's for 3D games):

Afterwards we can drag the background image from the Project Area onto the Background:

If we press Play then we can now see our space background, which is still very dark:

The Unlit Shader

The background is dark because it currently uses the Standard Shader, which only makes things bright if there are lights in the Scene. We won't use any kind of lights or shadows, so let's select the Unlit->Texture Shader:

If we press Play again then we can now see the background stars without being too dark:

UV Mapping

If we take a closer look at the Shader properties then we can already see our UV Tiling and Offset here:

Feel free to play around with those properties and see how they change the background. Tiling will repeat it and Offset will change the texture's position. If we set the y Offset to values like 0.1, 0.2, 0.3 and so on then we can already see the scrolling happen.

Of course, we don't want to change the offset manually 60 times per second in order to achieve a scrolling effect. We will write a Script that takes care of it. Let's click on the Add Component Button on the Quad, then select New Script, name it UVScroll and select CSharp for the language:

Unity just created a new C# Script in our Project Area and added it to the Quad. Let's create a new Scripts folder in our Project Area and move the Script into it:

Now we can double click the Script in order to open it:

using UnityEngine;

using System.Collections;



public class UVScroll : MonoBehaviour {



    // Use this for initialization

    void Start () {



    }



    // Update is called once per frame

    void Update () {



    }

}

We won't need the Start or the Update function so let's remove them. It's considered best practice to modify the UV Mapping in the LateUpdate function after all other calculations were finished. We will also add a public variable that let's us modify the Scroll Speed in the Inspector later on:

using UnityEngine;

using System.Collections;



public class UVScroll : MonoBehaviour {

    public Vector2 speed;



    void LateUpdate() {

        GetComponent<Renderer>().material.mainTextureOffset = speed * Time.time;

    }

}

Let's save the Script and then take a look at the Inspector again. Now we can modify the Speed. We will set the y speed (for vertical scrolling) to our wished speed and leave the x speed (horizontal scrolling) at 0 so it does not scroll horizontally at all:

The Scrolling Space Texture

If we press Play then we can now see our background scrolling downwards, just as if we were flying through space:

This effect is pretty good, but we will go one step further and implement Parallax Scrolling to add even more depth to it.