Systems

Systems own cross-entity logic. They iterate components across multiple entities.

Built-in Systems

Rendering

System	Purpose
Renderer3DSystem	Collects MeshRenderer + Transform3D, builds RenderCommandList
Renderer2DSystem	Renders SpriteRenderer entities via the 2D renderer
Camera3DSystem	Updates 3D view/projection matrices, pushes SetCamera command
Camera2DSystem	Updates the active 2D camera
InstancedTerrainSystem	Renders instanced terrain via DrawMeshInstanced commands
UISystem	Manages UI layers and widget rendering

Physics

System	Purpose
Physics3DSystem	3D collision detection, character controller, capsule vs AABB
Physics2DSystem	2D collision detection
RigidBody3DSystem	Integrates rigid body velocities and applies forces
DoorSystem	Updates hinge and linear joints with damping and angle/distance limits

Environment

System	Purpose
DayNightSystem	Drives day/night cycle, updates sun direction, sky colors, ambient light, fog
WindSystem	Advances wind time, modulates intensity with layered gusts
WeatherSystem	Manages weather state transitions (Clear/Cloudy/Rain/Snow/Storm/Fog)
PrecipitationSystem	Renders rain and snow particles
SeasonSystem	Updates seasonal parameters
EnvironmentalSystem	Base environmental simulation
AtmosphericEnvironmentalSystem	Extends EnvironmentalSystem for atmospheric physics

Transform & Hierarchy

System	Purpose
Transform3DSystem	Updates Transform3D world matrices from parent/child hierarchy
HierarchySystem	Updates Transform2D world matrices based on 2D hierarchy

Input & Audio

System	Purpose
InputMapSystem	Processes input bindings and dispatches input actions
AudioSystem	Manages audio playback, stops sources on entity destroy

Custom Systems

use PHPolygon\ECS\AbstractSystem;
use PHPolygon\ECS\World;

class DamageSystem extends AbstractSystem
{
    public function update(World $world, float $dt): void
    {
        foreach ($world->query(Health::class, DamageReceiver::class) as $entity) {
            $health = $entity->get(Health::class);
            $receiver = $entity->get(DamageReceiver::class);

            foreach ($receiver->pendingDamage as $damage) {
                $health->damage($damage);
            }
            $receiver->pendingDamage = [];

            if ($health->isDead()) {
                $world->destroyEntity($entity->id);
            }
        }
    }
}

System Phases

Systems execute in defined phases via the SystemPhase enum:

Phase	When	Typical use
PreUpdate	Before main update	Input processing, physics preparation
Update	Main game logic	Gameplay systems, AI, animation
Render	After update	Camera, renderer, UI systems
PostUpdate	After render	Cleanup, event dispatch

Naming Convention

System classes use noun + System suffix: Renderer3DSystem, Physics3DSystem.