Note: The source code to Bubble Racing and a living version of this tutorial can be found here.

Err, OK. Not that seeker. (Did anyone else watch that show?)

This seeker will be a hidden helper within our game. It tries to get to a target_position, but it will be stopped by walls and other such things. The behavior will come in handy, and we’ll use it later to make bubbles and fish.

Make the Seeker class

So really the Seeker is all about the code. But we will give the seeker a face regardless, mostly because it will make the test in the next section look better. Here comes a numbered list!

1. Make a new folder called seeker
2. Make a new Scene named Seeker, and save it in the seeker folder.
3. Pick 2DNode to start with, but you’ll have to change to root node to RigidPhysicsBody
4. Download this image of a charming broomstick riding individual from above and move it to the seeker folder.
5. Drag the charming broomstick riding individual into your Seeker scene.
6. Click on the funny little parchment paper on the top left. It’s the one with a green x.
7. Go with the default options, but save the new script in the seeker folder.
8. Copy and paste this fine code:

extends RigidBody2D

# Affects how long it takes for an object to go from 0 to max velocity
# Larger number = faster acceleration
var acceleration = 30

# This is the force of friction, which is always trying to bring an 
# object to a stop. Larger number = more friction
var linearDamp = 3

# Once the seeker is within this X pixels of the target, it starts to slow down
# to avoid overshooting the target_position
var throttle_dist = 150

## The x,y coordinates that the seeker should be trying to reach
var target_position = Vector2(0 ,0)

# Called when the node enters the scene tree for the first time.
func _ready():
	set_linear_damp(linearDamp)
	target_position = position

# Move towards target position
func _process(_delta):
	var vector = (target_position - position).normalized()
	var dist = target_position.distance_to(position)
	var throttle = min(dist, throttle_dist) / throttle_dist
	var impulse = vector * acceleration * throttle
	apply_central_impulse(impulse)

Test it Out

To test our seeker out, we’re going to build a little obsticle course. Then we’re going to tell the seeker to fly around completely at random. Nice.

1. Create a new Scened named SeekerTest. Save it in the seeker folder.
2. Drag some walls into the scene. We can’t let those walls be slacking off, now can we?
3. Drag a Seeker into the scene.
4. Create a new script for SeekerTest and copy and paste this script:

extends Node2D

var rng = RandomNumberGenerator.new()

func _on_Timer_timeout():
	var x = rng.randi_range(100, 400)
	var y = rng.randi_range(100, 400)
	$Seeker.target_position = Vector2(x, y)

5. Add a Timer to the scene, and set the timer to automatically start.
6. Link the timer’s timeout signal to the SeekerTest script. This will run the code in that timeout handler once per second (by default).
7. Hit the Play Scene button on the top right to send our charming broomstick riding individual flying.
8. Congratulations! You now have done a thing.