# Core Engine

The `simvx.core` package is the backend-agnostic foundation of SimVX. It provides the node system, scene tree, and all gameplay systems — no rendering dependency required.

## Subsystems

| System | Guide | Description |
|--------|-------|-------------|
| Nodes | {doc}`nodes` | Scene tree hierarchy, lifecycle, properties, signals, groups, coroutines |
| Animation | {doc}`animation` | Tweens, sprite sheets, keyframe clips, state machines |
| Audio | {doc}`audio` | 2D/3D spatial audio, buses, resource caching |
| UI | {doc}`ui` | Controls, containers, theming, focus management |
| Math | {doc}`math` | Vec2, Vec3, Quat, and matrix utilities (pure NumPy) |
| Collision | {doc}`physics` | GJK narrowphase, AABB broadphase, raycasting |
| Scenes | {doc}`scenes` | JSON serialization, PackedScene prefabs |
| Particles | {doc}`particles` | Particle emitter with CPU and GPU simulation modes |
| TileMap | {doc}`tilemap` | Grid-based 2D level design with auto-tiling |
| Navigation | {doc}`navigation` | A* pathfinding (graph and grid) with steering agents |
| Skeleton | {doc}`skeleton` | Bone hierarchy and joint matrices for GPU skinning |
| Physics Engine | {doc}`physics_engine` | Rigid body dynamics, forces, joints, collision response |

## API Reference

See {py:mod}`simvx.core` for the complete API.