PLECK lesson 21 · suggested week 5, day 1

Detect an overlap without blocking movement

Objective. Build an Area2D pickup and explain body_entered.

Godot Engine Standard desktop editor 4.7.2-stable, GDScript (Godot 4), Compatibility renderer. Headless Godot 4.7.2.stable.official.ed1daf0bf passed 106 assertions on the supplied scaffolds, including malformed JSON saves. Audio used the Dummy driver and a synthetic WAV, not a speaker. The visual editor, browser export, and signed-in submission were not tested. The desk still does not run a student's own upload.

About 55 minutes. The due date is chosen by a parent.

Area2D signals, groups, exactly-once events and a HUD

Suggested pace: Recall and predict 5 min; Read instruction and scaffold 12 min; Build or design the assigned artifact 25 min; Run acceptance tests 8 min; Explain and checkpoint 5 min.

Materials: Godot Standard 4.7.2 desktop editor (GDScript, Compatibility renderer), Local course folder and prior checkpoint, No paid assets or public account required.

Comes after VGC-L020.

An Area2D senses overlaps but does not act as a solid wall. Build C-PICKUP with a circle collider and visible gold marker. It checks layer 1 because it only needs to notice the Player body. Add Player to the player group in the Node dock; groups express a role without depending on an instance’s exact name. The signal callback receives the entering body. Testing the group prevents a wall or another body from collecting the coin accidentally.

Worked example

A pickup emits collected(1); a manager receives that event and changes one score variable. The label formats that score rather than keeping a second independent total. Scaffold C-PICKUP — An exactly-once pickup signal Setup: Create Area2D root Coin, CollisionShape2D Circle radius 10. Layer 3 (bit value 4), mask layer 1 only. Monitoring on. Attach script and save Coin.tscn. In the Node > Groups editor add Player root to group player. Put a Coin instance and Player instance in World. Manager connects each Coin.collected to its score handler (see C-MANAGER). Signal wiring here is code-only: do not also connect body_entered in editor. ```gdscript extends Area2D signal collected(points: int) @export var points: int = 1 var taken: bool = false func _ready() -> void: body_entered.connect(_on_body_entered) func _draw() -> void: draw_circle(Vector2.ZERO, 10.0, Color.GOLD) draw_line(Vector2(-5, 0), Vector2(5, 0), Color.BLACK, 2.0) func _on_body_entered(body: Node2D) -> void: if taken or not body.is_in_group("player"): return taken = true collected.emit(points) queue_free() ```

An exactly-once pickup signal

GDScript (Godot 4, not Scratch, Python, JavaScript or C#). Scaffold C-PICKUP. Copy starts from this text. The desk does not run it.

Scene and node setup

Create Area2D root Coin, CollisionShape2D Circle radius 10. Layer 3 (bit value 4), mask layer 1 only. Monitoring on. Attach script and save Coin.tscn. In the Node > Groups editor add Player root to group player. Put a Coin instance and Player instance in World. Manager connects each Coin.collected to its score handler (see C-MANAGER). Signal wiring here is code-only: do not also connect body_entered in editor.

extends Area2D
signal collected(points: int)
@export var points: int = 1
var taken: bool = false
func _ready() -> void:
    body_entered.connect(_on_body_entered)
func _draw() -> void:
    draw_circle(Vector2.ZERO, 10.0, Color.GOLD)
    draw_line(Vector2(-5, 0), Vector2(5, 0), Color.BLACK, 2.0)
func _on_body_entered(body: Node2D) -> void:
    if taken or not body.is_in_group("player"):
        return
    taken = true
    collected.emit(points)
    queue_free()

Checks to run in the editor

A player touching the coin emits once and removes it.
A wall or hazard touching the coin does not collect.

Native Godot 4.7.2.stable.official.ed1daf0bf headless compile and representative node-tree/runtime tests passed; see native-qa-results.json. Visual UI, audible output, exports and website submission still need separate checks.

Pocket Orchard starter, as text files. Open the files in Godot on the family computer. This page does not download a zip or run the project.

Detect an overlap without blocking movement — evidence task

1. Create Coin.tscn and put one instance on a reachable route.
2. Add Player to group player and test collection.

Deliverable. Coin source and one-coin overlap test note.

Acceptance checks

VGC-L021-T1. Player passes through the coin’s position.
VGC-L021-T2. Only a body in player group makes the coin disappear.

Understanding question. Why use Area2D rather than StaticBody2D for a collectible?

Include a downloadable project ZIP with project.godot, .tscn, .gd and original asset files when code changes. A private, teacher-accessible download link to that ZIP is equivalent. Screenshots or a playthrough do not replace editable source.

If this is still shaky. Use one coin and one player in a blank World. Confirm the group and mask before adding a score label. Start with the first assigned task and re-run its acceptance test before adding the remaining feature.

Optional extra. Add a second pickup value using the same signal instead of duplicating the whole scene. Document one changed parameter, your prediction, and the observed effect; optional, not required for completion.

Turn in typed notes and a JPEG, PNG, or WebP screenshot. One https address is stored as text and is not opened, extracted, or run. An MP3, WAV, M4A, MP4, or WebM file up to 4 MB can show a demo. The demo does not replace editable source. Zip and code files are refused. If there is no private link, keep the project on the family computer and review the code in person.

Godot step by step: nodes, scenes, GDScript, input, signals
Free public documentation, no account. Same class help is available within the desktop editor.
· Opening this link does not submit the lesson.

This is a preview. A parent assigns the lesson and chooses the due date after the student is enrolled. The answer key is not on this page.

Print this lesson