Brake and Drag

Lesson 3 of 20 in Coddy's Godot Game: Neon Circuit course.

Let go of Up and the car rolls on forever. Two things fix that.

Drag slows a moving car a little every frame. Take 60 percent of the velocity away each second:

velocity *= 1.0 - drag * delta

And Down brakes. Read Up and Down together, so the throttle goes from -1 to 1. While the car still rolls forward, Down pushes back harder than the engine pushes forward. Once it stops, Down reverses:

var throttle := Input.get_axis("move_down", "move_up")
if throttle < 0.0 and speed > 10.0:
	velocity += forward * throttle * accel * 1.6 * delta
else:
	velocity += forward * throttle * accel * delta

Challenge

Easy

Add @export var drag := 0.6.
Read the throttle with get_axis as above.
Replace the line that grows the velocity with the if and else.
Before limit_length, apply the drag.

Try it yourself

extends Node2D

@export var accel := 260.0
@export var max_speed := 200.0
@export var turn_speed := 3.2

var velocity := Vector2.ZERO


func _physics_process(delta: float) -> void:
	var throttle := Input.get_action_strength("move_up")
	var steer := Input.get_axis("move_left", "move_right")

	var forward := Vector2.RIGHT.rotated(rotation)
	var speed := velocity.dot(forward)

	velocity += forward * throttle * accel * delta
	rotation += steer * turn_speed * delta * clampf(absf(speed) / 90.0, 0.0, 1.0) * signf(speed + 0.01)
	velocity = velocity.limit_length(max_speed)
	position += velocity * delta
	$Exhaust.emitting = throttle > 0.0