Listening to player input¶
Building upon the previous lesson Creating your first script, let's look
at another important feature of any game: giving control to the player.
To add this, we need to modify our
You have two main tools to process the player's input in Godot:
The built-in input callbacks, mainly
_process(), it's a built-in virtual function that Godot calls every time the player presses a key. It's the tool you want to use to react to events that don't happen every frame, like pressing Space to jump. To learn more about input callbacks, see Using InputEvent.
Inputsingleton. A singleton is a globally accessible object. Godot provides access to several in scripts. It's the right tool to check for input every frame.
We're going to use the
Input singleton here as we need to know if the player
wants to turn or move every frame.
For turning, we should use a new variable:
direction. In our
function, replace the
rotation += angular_speed * delta line with the
var direction = 0 if Input.is_action_pressed("ui_left"): direction = -1 if Input.is_action_pressed("ui_right"): direction = 1 rotation += angular_speed * direction * delta
direction local variable is a multiplier representing the direction in
which the player wants to turn. A value of
0 means the player isn't pressing
the left or the right arrow key. A value of
1 means the player wants to turn
-1 means they want to turn left.
To produce these values, we introduce conditions and the use of
condition starts with the
if keyword in GDScript and ends with a colon. The
condition is the expression between the keyword and the end of the line.
To check if a key was pressed this frame, we call
The method takes a text string representing an input action and returns
if the action is pressed,
The two actions we use above, "ui_left" and "ui_right", are predefined in every Godot project. They respectively trigger when the player presses the left and right arrows on the keyboard or left and right on a gamepad's D-pad.
You can see and edit input actions in your project by going to Project -> Project Settings and clicking on the Input Map tab.
Finally, we use the
direction as a multiplier when we update the node's
rotation += angular_speed * direction * delta.
If you run the scene with this code, the icon should rotate when you press Left and Right.
Moving when pressing "up"¶
To only move when pressing a key, we need to modify the code that calculates the
velocity. Replace the line starting with
var velocity with the code below.
var velocity = Vector2.ZERO if Input.is_action_pressed("ui_up"): velocity = Vector2.UP.rotated(rotation) * speed
We initialize the
velocity with a value of
constant of the built-in
Vector type representing a 2D vector of length 0.
If the player presses the "ui_up" action, we then update the velocity's value, causing the sprite to move forward.
Here is the complete
Sprite.gd file for reference.
extends Sprite var speed = 400 var angular_speed = PI func _process(delta): var direction = 0 if Input.is_action_pressed("ui_left"): direction = -1 if Input.is_action_pressed("ui_right"): direction = 1 rotation += angular_speed * direction * delta var velocity = Vector2.ZERO if Input.is_action_pressed("ui_up"): velocity = Vector2.UP.rotated(rotation) * speed position += velocity * delta
If you run the scene, you should now be able to rotate with the left and right arrow keys and move forward by pressing Up.
In summary, every script in Godot represents a class and extends one of the
engine's built-in classes. The node types your classes inherit from give you
access to properties like
position in our sprite's case.
You also inherit many functions, which we didn't get to use in this example.
In GDScript, the variables you put at the top of the file are your class's properties, also called member variables. Besides variables, you can define functions, which, for the most part, will be your classes' methods.
Godot provides several virtual functions you can define to connect your class
with the engine. These include
_process(), to apply changes to the node
every frame, and
_unhandled_input(), to receive input events like key and
button presses from the users. There are quite a few more.
Input singleton allows you to react to the players' input anywhere in
your code. In particular, you'll get to use it in the
In the next lesson Using signals, we'll build upon the relationship between scripts and nodes by having our nodes trigger code in scripts.