Phase 0 of the gameplay-controller work (#57): turn the static Collision.*
overlap tests into a real physics-lite moving-body-with-collision layer that
the platformer / shooter / NPC-AI / RPG families build on.
New engine-owned system esys_move (runtime/native/systems_move.ludic), spliced
and Update-phase-registered when a game declares `Body` (parse.ludic), standing
entirely on the reflection ABI like the SpriteAnim / Motion / Light2D systems:
- Body { vx, vy, gravity, max_fall, rx, ry, policy, on_ground, hit_wall,
hit_ceiling } — Q16.16 velocity + engine-owned sub-pixel accumulators.
- Collider { w, h, offx, offy, is_trigger, one_way, layer, mask, hit, entered,
exited } — AABB shape off Position, layer/mask filtering, one-way + triggers.
- Solids { tile, wall, oneway } — optional config entity enabling the tile-grid
broadphase over the Map.* tilemap.
esys_move integrates velocity + gravity, then resolves per-axis swept AABB
against both solid Collider entities and the tile grid (no tunneling), handles
one-way platforms (block only a downward landing), reports trigger/sensor
overlaps without resolving, and sets on_ground / hit_wall / hit_ceiling for a
controller to poll. No float, no hidden singletons, no runtime dispatch —
integer + deterministic, so replay / lockstep / world_save hold. Contact is
surfaced as polled flags (the SpriteAnim.event_fired shape), so a game raises
its own CollisionResolved / TriggerEntered events with no engine coupling.
Two self-asserting examples (entity + tile broadphase) wired into `x test`;
docs added to the collision section. A build with no Body compiles byte-for-byte
the same (bootstrap fixpoint + all golden renders unchanged).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
