Combat basics skill for AI agents

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When your agent uses it

• Adding attacks, health and damage, or enemies that can be hit and hit back
• Adding projectiles or bullets — homing, piercing, area-of-effect, or pooling hundreds of them
• Wiring death and respawn, or debugging hits that never land or friendly fire

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Install

npx -y summer-engine@latest skills install combat-basics --agent claude-code

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The skill

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The layer model (set this up first)

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Health component (reuse everywhere)

class_name Health extends Node

signal damaged(amount: int, current: int)
signal died

@export var max_health: int = 100
var current: int

func _ready() -> void:
	current = max_health

func take_damage(amount: int) -> void:
	if current <= 0:
		return
	current = maxi(0, current - amount)
	damaged.emit(amount, current)
	if current == 0:
		died.emit()

func heal(amount: int) -> void:
	current = mini(max_health, current + amount)

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Hurtbox -> Health

extends Area2D   # Hurtbox, child of the character

@export var health_path: NodePath
@onready var health: Health = get_node(health_path)

func _ready() -> void:
	area_entered.connect(_on_area_entered)

func _on_area_entered(hitbox: Area2D) -> void:
	if hitbox.has_method("get_damage"):
		health.take_damage(hitbox.get_damage())

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Hitbox

extends Area2D   # Hitbox, child of weapon or attack

@export var damage: int = 10
func get_damage() -> int:
	return damage

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Death, knockback, feedback

• On died: queue_free(), spawn a death VFX, drop loot, add_kill() on your game manager. For the player, switch to a GAME_OVER state instead of freeing.
• Knockback: push the victim velocity = (victim.global_position - attacker.global_position).normalized() * force, decay it each frame.
• Every hit needs feedback or it reads as broken: a flash (modulate to white for 0.05s), a damage number (floating Label), a small screen shake, a hitstop (Engine.time_scale = 0.05 for one frame). Silent damage feels like a no-op.

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Projectiles (short version)

extends Area2D   # projectile

@export var speed: float = 600.0
@export var damage: int = 15
var direction: Vector2 = Vector2.RIGHT

func _ready() -> void:
	body_entered.connect(_on_hit)
	get_tree().create_timer(3.0).timeout.connect(queue_free)  # lifetime

func _physics_process(delta: float) -> void:
	position += direction * speed * delta

func _on_hit(body: Node) -> void:
	if body.has_node("Health"):
		body.get_node("Health").take_damage(damage)
	queue_free()

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Traps

• Hitbox on the wrong layer/mask = no hits or friendly fire. Verify the layer table above before debugging the scripts.
• Two Areas with neither monitoring nor monitorable never report overlap.
• Freeing a node mid-signal can error - defer with queue_free() (safe), not free().
• Damaging in _process instead of on overlap = continuous per-frame damage.

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Applying it in Summer Engine

• Scripts (health.gd, hurtbox.gd, hitbox.gd, projectile.gd) are files: create with summer_write_file(path=..., content=..., create_only=true), change with summer_replace_text. Check each with summer_get_script_errors.
• Nodes (the Area, its CollisionShape, the Health child) are scene mutations: summer_add_node / summer_set_prop with scenePath, or one summer_batch with AddNode / SetProp ops so the scene saves once. Set collision_layer and collision_mask as integers (bit values), not layer names.
• Prove a hit with a RunVerification probe (see playtesting-a-feature): spawn or find one enemy, press the attack action, report() the enemy’s Health.current before and after. A static scene check cannot show that a hit registered.

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From a shell

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Files in this skill

• references/projectiles-and-aoe.md

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Related skills

• make-game: Orchestrate ‘make me a game’: brainstorm, plan, scaffold, mechanics, art, audio, polish, verify, ship.
• character-movement: Player controllers for 2D and 3D, plus the standard third-person controller for Summer humanoids.
• game-feel: Add juice: hit-flash, trauma camera shake and audio ducking, one hit fires all three.
• auto-fire-targeting: Fix auto-fire targeting (survivors, ARPG, tower defense) with pending damage to stop overkill.
• design-npc: Design enemy, NPC, boss or companion behavior: perception, state machine, telegraphs, script stub.