.. Intention: - Giving a *short* and sweet hands-on intro to GDScript. The page should focus on working in the code editor. - We assume the reader has programming foundations. If you don't, consider taking the course we recommend in the :ref:`introduction to Godot page `. Techniques: - Creating a sprite. - Creating a script. - _init() and _process(). - Moving an object on screen. .. _doc_scripting_first_script: Creating your first script ========================== In this lesson, you will code your first script to make the Godot icon turn in circles using GDScript. As we mentioned :ref:`in the introduction `, we assume you have programming foundations. The equivalent C# code has been included in another tab for convenience. .. image:: img/scripting_first_script_rotating_godot.gif .. seealso:: To learn more about GDScript, its keywords, and its syntax, head to the :ref:`GDScript reference`. .. seealso:: To learn more about C#, head to the :ref:`C# basics ` page. Project setup ------------- Please :ref:`create a new project ` to start with a clean slate. Your project should contain one picture: the Godot icon, which we often use for prototyping in the community. .. Godot icon We need to create a Sprite2D node to display it in the game. In the Scene dock, click the Other Node button. .. image:: img/scripting_first_script_click_other_node.webp Type "Sprite2D" in the search bar to filter nodes and double-click on Sprite2D to create the node. .. image:: img/scripting_first_script_add_sprite_node.webp Your Scene tab should now only have a Sprite2D node. .. image:: img/scripting_first_script_scene_tree.webp A Sprite2D node needs a texture to display. In the Inspector on the right, you can see that the Texture property says "[empty]". To display the Godot icon, click and drag the file ``icon.svg`` from the FileSystem dock onto the Texture slot. .. image:: img/scripting_first_script_setting_texture.webp .. note:: You can create Sprite2D nodes automatically by dragging and dropping images on the viewport. Then, click and drag the icon in the viewport to center it in the game view. .. image:: img/scripting_first_script_centering_sprite.webp Creating a new script --------------------- To create and attach a new script to our node, right-click on Sprite2D in the scene dock and select "Attach Script". .. image:: img/scripting_first_script_attach_script.webp The Attach Node Script window appears. It allows you to select the script's language and file path, among other options. Change the Template field from "Node: Default" to "Object: Empty" to start with a clean file. Leave the other options set to their default values and click the Create button to create the script. .. image:: img/scripting_first_script_attach_node_script.webp The Script workspace should appear with your new ``sprite_2d.gd`` file open and the following line of code: .. tabs:: .. code-tab:: gdscript GDScript extends Sprite2D .. code-tab:: csharp C# using Godot; public partial class MySprite2D : Sprite2D { } Every GDScript file is implicitly a class. The ``extends`` keyword defines the class this script inherits or extends. In this case, it's ``Sprite2D``, meaning our script will get access to all the properties and functions of the Sprite2D node, including classes it extends, like ``Node2D``, ``CanvasItem``, and ``Node``. .. note:: In GDScript, if you omit the line with the ``extends`` keyword, your class will implicitly extend :ref:`RefCounted `, which Godot uses to manage your application's memory. Inherited properties include the ones you can see in the Inspector dock, like our node's ``texture``. .. note:: By default, the Inspector displays a node's properties in "Title Case", with capitalized words separated by a space. In GDScript code, these properties are in "snake_case", which is lowercase with words separated by an underscore. You can hover over any property's name in the Inspector to see a description and its identifier in code. Hello, world! ------------- Our script currently doesn't do anything. Let's make it print the text "Hello, world!" to the Output bottom panel to get started. Add the following code to your script: .. tabs:: .. code-tab:: gdscript GDScript func _init(): print("Hello, world!") .. code-tab:: csharp C# public MySprite2D() { GD.Print("Hello, world!"); } Let's break it down. The ``func`` keyword defines a new function named ``_init``. This is a special name for our class's constructor. The engine calls ``_init()`` on every object or node upon creating it in memory, if you define this function. .. note:: GDScript is an indent-based language. The tab at the start of the line that says ``print()`` is necessary for the code to work. If you omit it or don't indent a line correctly, the editor will highlight it in red and display the following error message: "Indented block expected". Save the scene as ``sprite_2d.tscn`` if you haven't already, then press :kbd:`F6` (:kbd:`Cmd + R` on macOS) to run it. Look at the **Output** bottom panel that expands. It should display "Hello, world!". .. image:: img/scripting_first_script_print_hello_world.webp Delete the ``_init()`` function, so you're only left with the line ``extends Sprite2D``. Turning around -------------- It's time to make our node move and rotate. To do so, we're going to add two member variables to our script: the movement speed in pixels per second and the angular speed in radians per second. Add the following after the ``extends Sprite2D`` line. .. tabs:: .. code-tab:: gdscript GDScript var speed = 400 var angular_speed = PI .. code-tab:: csharp C# private int _speed = 400; private float _angularSpeed = Mathf.Pi; Member variables sit near the top of the script, after any "extends" lines, but before functions. Every node instance with this script attached to it will have its own copy of the ``speed`` and ``angular_speed`` properties. .. note:: Angles in Godot work in radians by default, but you have built-in functions and properties available if you prefer to calculate angles in degrees instead. To move our icon, we need to update its position and rotation every frame in the game loop. We can use the ``_process()`` virtual function of the ``Node`` class. If you define it in any class that extends the Node class, like Sprite2D, Godot will call the function every frame and pass it an argument named ``delta``, the time elapsed since the last frame. .. note:: Games work by rendering many images per second, each called a frame, and they do so in a loop. We measure the rate at which a game produces images in Frames Per Second (FPS). Most games aim for 60 FPS, although you might find figures like 30 FPS on slower mobile devices or 90 to 240 for virtual reality games. The engine and game developers do their best to update the game world and render images at a constant time interval, but there are always small variations in frame render times. That's why the engine provides us with this delta time value, making our motion independent of our framerate. At the bottom of the script, define the function: .. tabs:: .. code-tab:: gdscript GDScript func _process(delta): rotation += angular_speed * delta .. code-tab:: csharp C# public override void _Process(double delta) { Rotation += _angularSpeed * (float)delta; } The ``func`` keyword defines a new function. After it, we have to write the function's name and arguments it takes in parentheses. A colon ends the definition, and the indented blocks that follow are the function's content or instructions. .. note:: Notice how ``_process()``, like ``_init()``, starts with a leading underscore. By convention, Godot's virtual functions, that is to say, built-in functions you can override to communicate with the engine, start with an underscore. The line inside the function, ``rotation += angular_speed * delta``, increments our sprite's rotation every frame. Here, ``rotation`` is a property inherited from the class ``Node2D``, which ``Sprite2D`` extends. It controls the rotation of our node and works with radians. .. tip:: In the code editor, you can ctrl-click on any built-in property or function like ``position``, ``rotation``, or ``_process`` to open the corresponding documentation in a new tab. Run the scene to see the Godot icon turn in-place. .. image:: img/scripting_first_script_godot_turning_in_place.gif .. note:: In C#, notice how the ``delta`` argument taken by ``_Process()`` is a ``double``. We therefore need to convert it to ``float`` when we apply it to the rotation. Moving forward ~~~~~~~~~~~~~~ Let's now make the node move. Add the following two lines inside of the ``_process()`` function, ensuring the new lines are indented the same way as the ``rotation += angular_speed * delta`` line before them. .. tabs:: .. code-tab:: gdscript GDScript var velocity = Vector2.UP.rotated(rotation) * speed position += velocity * delta .. code-tab:: csharp C# var velocity = Vector2.Up.Rotated(Rotation) * _speed; Position += velocity * (float)delta; As we already saw, the ``var`` keyword defines a new variable. If you put it at the top of the script, it defines a property of the class. Inside a function, it defines a local variable: it only exists within the function's scope. We define a local variable named ``velocity``, a 2D vector representing both a direction and a speed. To make the node move forward, we start from the Vector2 class's constant ``Vector2.UP``, a vector pointing up, and rotate it by calling the Vector2 method ``rotated()``. This expression, ``Vector2.UP.rotated(rotation)``, is a vector pointing forward relative to our icon. Multiplied by our ``speed`` property, it gives us a velocity we can use to move the node forward. We add ``velocity * delta`` to the node's ``position`` to move it. The position itself is of type :ref:`Vector2 `, a built-in type in Godot representing a 2D vector. Run the scene to see the Godot head run in circles. .. image:: img/scripting_first_script_rotating_godot.gif .. note:: Moving a node like that does not take into account colliding with walls or the floor. In :ref:`doc_your_first_2d_game`, you will learn another approach to moving objects while detecting collisions. Our node currently moves by itself. In the next part, :ref:`doc_scripting_player_input`, we'll use player input to control it. Complete script --------------- Here is the complete ``sprite_2d.gd`` file for reference. .. tabs:: .. code-tab:: gdscript GDScript extends Sprite2D var speed = 400 var angular_speed = PI func _process(delta): rotation += angular_speed * delta var velocity = Vector2.UP.rotated(rotation) * speed position += velocity * delta .. code-tab:: csharp C# using Godot; public partial class MySprite2D : Sprite2D { private int _speed = 400; private float _angularSpeed = Mathf.Pi; public override void _Process(double delta) { Rotation += _angularSpeed * (float)delta; var velocity = Vector2.Up.Rotated(Rotation) * _speed; Position += velocity * (float)delta; } }