Projectile Component

ProjectileComponent marks an entity as a projectile and stores its damage value and the entity that fired it.

ProjectileComponent

struct ProjectileComponent: Component {
    var damage: Float
    var owner: Entity
}

Property	Type	Description
damage	Float	Hit-point damage dealt on impact
owner	Entity	The entity that fired this projectile (used to avoid self-damage)

Creating a Projectile Entity

Projectiles are created via EntityFactory.makeProjectile:

EntityFactory.makeProjectile(
    from: ownerTransform.position,
    aimAt: fireDirection,
    speed: speedWhenFired,
    owner: ownerEntity,
    in: world
)

These components attache to the new entity (the projectile):

Component	Value
TransformComponent	Spawns at the given position; rotation derived from direction
VelocityComponent	direction * speed
SpriteComponent	"normalHandgunBullet", z-position 5
ProjectileComponent	damage in factory method: 10, owner: ownerEntity
EffectiveRangeComponent	base in factory method: 400 units
CollisionBoxComponent	6 × 6 point hitbox

Lifetime

A projectile is destroyed when either:

1. Range is exhausted — EffectiveRangeComponent.value.current reaches 0 (base range: 400 units).
2. It hits a solid — the CollisionEventBuffer emits a projectileHitSolid event for it.

Both cases enqueue the entity in DestructionQueue, which flushes at the end of ProjectileSystem.update.

In future iterations, we want to add a third case for hitting a damageable entity (e.g. an enemy), but currently projectiles pass through enemies without collision.

ProjectileSystem

ProjectileSystem runs at priority: 60 — after WeaponSystem (priority 50) so any newly spawned projectiles are already in the world when movement is applied.

Each frame it:

1. Moves every projectile by velocity × deltaTime.
2. Decrements EffectiveRangeComponent by the distance traveled; enqueues expired projectiles.
3. Reads CollisionEventBuffer.projectileHitSolid and enqueues all hit projectiles.
4. Flushes DestructionQueue.

Dependencies

Dependency	Role
VelocityComponent	Stores the projectile's linear velocity vector
EffectiveRangeComponent	Tracks remaining travel distance before auto-destruction
CollisionBoxComponent	Defines the hitbox for wall/solid collision detection
CollisionEventBuffer	Source of projectileHitSolid events
DestructionQueue	Deferred entity removal to avoid mutating the world mid-iteration
EntityFactory	Factory method for creating projectile entities