Diagnose a collision systematically

Worked example

A wall is a StaticBody2D with matching rectangle art and collider. A player standing next to it should be stopped by geometry, not by a special if statement checking the wall’s screen color. Scaffold C-BODY — Reusable top-down player with collision Setup: Create CharacterBody2D root Player at (80,180); add CollisionShape2D with CircleShape2D radius 14. Attach this script to Player and save Player.tscn. Use C-FREE-MOVE input actions. Root collision layer 1, mask 2. Create a separate StaticBody2D Wall on layer 2 mask 1 with RectangleShape2D collision and a Polygon2D rectangle as visible child. Instance both under an unscaled Node2D World. Do not put a body inside another physics body. ```gdscript extends CharacterBody2D @export var speed: float = 160.0 func _draw() -> void: draw_circle(Vector2.ZERO, 14.0, Color.CORNFLOWER_BLUE) draw_line(Vector2(-8, 0), Vector2(8, 0), Color.WHITE, 3.0) func _physics_process(_delta: float) -> void: velocity = Input.get_vector("move_left", "move_right", "move_up", "move_down") * speed move_and_slide() ```

Reusable top-down player with collision

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

Scene and node setup

Create CharacterBody2D root Player at (80,180); add CollisionShape2D with CircleShape2D radius 14. Attach this script to Player and save Player.tscn. Use C-FREE-MOVE input actions. Root collision layer 1, mask 2. Create a separate StaticBody2D Wall on layer 2 mask 1 with RectangleShape2D collision and a Polygon2D rectangle as visible child. Instance both under an unscaled Node2D World. Do not put a body inside another physics body.

extends CharacterBody2D
@export var speed: float = 160.0
func _draw() -> void:
    draw_circle(Vector2.ZERO, 14.0, Color.CORNFLOWER_BLUE)
    draw_line(Vector2(-8, 0), Vector2(8, 0), Color.WHITE, 3.0)
func _physics_process(_delta: float) -> void:
    velocity = Input.get_vector("move_left", "move_right", "move_up", "move_down") * speed
    move_and_slide()

Checks to run in the editor

• Player stops at the wall rather than passing through.
• Diagonal speed matches horizontal speed.
• Do not multiply velocity by delta before move_and_slide.

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.

Diagnose a collision systematically — evidence task

1. 1. Introduce one known fault: disable the wall collider.
2. 2. Write a four-part report, verify the cause, restore the collider and repeat the same action.

Deliverable. Bug report and fixed project checkpoint.

Acceptance checks

• VGC-L019-T1. The report reproduces the failure from a fresh run.
• VGC-L019-T2. The identical test passes after the single fix.

Understanding question. Why should the same reproduction steps be used after the fix?

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 a single rectangle wall and C-BODY. Enable visible collision shapes in the Debug menu before redesigning the level. Start with the first assigned task and re-run its acceptance test before adding the remaining feature.

Optional extra. Compare two collider sizes and explain how perceived fairness changes. 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.

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