feat: bees and frogs

AGENTS.md

@@ -77,28 +77,44 @@ rules live in `.agents/rules/*.md`.
     (procedural low-poly rock: a squashed, jittered, part-buried sphere;
     `Boulder.build` appends into a shared mesh), `Bush` (cluster of small leaf
     blobs, shares the oak leaf texture/mesh), `Flower` (thin stem + colored bloom;
-    samples a 2x2 color-atlas texture, drawn double-sided).
+    samples a 2x2 color-atlas texture, drawn double-sided), `Mob` (a **roaming**
+    creature — `frog` hops the ground, `bee` hovers/darts — the engine's only
+    moving geometry. Unlike the baked props, a mob's low-poly mesh is built once
+    per kind in **local space**; `Mob.build` bakes the two canonical meshes,
+    `Mob.update` steps the wander AI (leashed to a home anchor, deterministic via
+    an evolving per-mob seed) each frame, and the live `position`/`heading`/`scale`
+    become a per-frame model matrix at draw time).
 - `app/` — browser glue.
   - `main.ts` — game loop: input, sim, preset switching, per-frame culling, then
     the non-blocking pump (`renderer.dispatch`/`done`) + `present` (GPU/CSS
     upscale) + a multi-line frame HUD (`work + present` critical-path ms, vsync
     interval, visible chunks / LOD-aware tri count — the real profiler in play).
+    Also owns the **mob sim**: each frame it steps `Mob.update` for every mob,
+    rebuilds the near-player mob colliders into `level.colliders`, and culls the
+    mobs (`visibleMobs`) so only the visible transforms get dispatched.
   - `renderer.ts` — the render driver. When the page is cross-origin-isolated it
     runs a pool of `render-worker.ts` threads (`MAX_WORKERS`) over a
     `SharedArrayBuffer` framebuffer, each owning a disjoint row band, synced by a
     lock-free `Atomics` barrier; otherwise it renders inline. `dispatch`/`done`
-    are non-blocking so the caller paces on rAF. `?bench=st|mt` A/Bs the paths.
+    are non-blocking so the caller paces on rAF. Per-frame inputs ride shared
-  - `renderScene.ts` — `renderBand(fb, scene, …, y0, y1)`: the single source of
+    arrays: camera/matrix/visible-chunk list, plus the visible **mob transforms**
-    render truth (sky + room + culled chunks + sprite + quantize for a row band).
+    (`mobState`, count in the `MOBVIS` control slot). `?bench=st|mt` A/Bs the paths.
-    Used full-height by the inline path, per-band by each worker. `Scene` bundles
+  - `renderScene.ts` — `renderBand(fb, scene, …, mobDraws, …, y0, y1)`: the single
-    the meshes/textures so it clones to a worker whole.
+    source of render truth (sky + room + culled chunks + sprite + roaming mobs +
+    quantize for a row band). Used full-height by the inline path, per-band by each
+    worker. `Scene` bundles the static meshes/textures (incl. the two canonical mob
+    meshes) so it clones to a worker whole; each mob is drawn double-sided through
+    its own `viewProj × Mat4.compose(...)` model matrix, and `visibleMobs`
+    frustum-culls the moving mobs per frame.
   - `assets.ts` — load `/assets/*.png` → `Texture` (zero-copy; ImageData bytes
     are already the `Color` layout).
   - `level.ts` — builds the playground: a flat stone-floored room (three thick
     walls via `slab`, north side open) always drawn, in the center of a big grassy
     `Terrain` world (~20x across). Props are placed first (`placeTrees` /
     `placeBoulders` / `placeBushes` / `placeFlowers` → instance lists + colliders;
-    `TREE_/BOULDER_/BUSH_/FLOWER_COUNT`/`_SEED`/`_REACH`), then `buildChunks` bakes
+    `TREE_/BOULDER_/BUSH_/FLOWER_COUNT`/`_SEED`/`_REACH`) and the roaming mobs
+    scattered (`placeMobs`; `FROG_/BEE_COUNT`, `MOB_SEED`, `MOB_REACH` — mobs move,
+    so they carry no baked colliders), then `buildChunks` bakes
     terrain + props into a `CHUNK_GRID` x `CHUNK_GRID` grid of `Chunk`s (each =
     per-texture meshes grass/bark/leaf/needle/rock/flowers + a tight AABB) that
     `main` frustum-culls; bushes fold into the leaf mesh, flowers get their own
@@ -118,16 +134,19 @@ rules live in `.agents/rules/*.md`.
   `#fps` meter div (styled inline).
 - `scripts/gen-assets.ts` — procedurally draws the placeholder textures and
   writes PNGs (hand-rolled encoder via `node:zlib`). Run via `bun run assets`.
-- `assets/` — generated `floor/grass/bark/leaf/needle/rock/flower/wall/crate/npc`
+- `assets/` — generated `floor/grass/bark/leaf/needle/rock/flower/wall/crate/npc/frog/bee`
   PNGs (`floor` = room stone, `grass` = outdoor ground, `bark`/`leaf`/`needle` =
-  tree trunk/oak/spruce, `rock` = boulders, `flower` = 2x2 bloom-color atlas).
+  tree trunk/oak/spruce, `rock` = boulders, `flower` = 2x2 bloom-color atlas,
+  `frog`/`bee` = mob skin atlases: frog green + eye tone; bee stripe bands +
+  head-dark + wing-pale regions).
   Swap for real art anytime;
   filenames are the contract.
 - `server/` — Bun server stub. `shared/` — isomorphic slot.
 
 ## Frame pipeline (`app/main.ts` `tick`)
 
-`Player.update` → build `Camera` → `Camera.viewProjection` → `visibleChunks`
+`Mob.update` (all mobs) + rebuild near-player mob colliders → `Player.update` →
+build `Camera` → `Camera.viewProjection` → `visibleChunks` + `visibleMobs`
 (frustum-cull, once on the main thread) → `renderer.dispatch` (non-blocking) →
 next rAF: `renderer.done()` ? `present` : skip this vsync. Frame N is presented
 while N+1 is dispatched; the pump never blocks or async-awaits, so it can't
@@ -148,8 +167,9 @@ floor/walls/crate (room, always) → for each visible `Chunk` draw grass, then
 per chunk via the pure `chunkFar` test (dist² from camera to the chunk AABB vs
 `lodDistance²`) — either the full rock/bark/leaf/needle + flowers, or the cheap
 `rockFar/barkFar/needleFar/leafFar` impostor meshes (foliage detail dropped).
-All backface-culled except double-sided flowers → `Sprite.billboard(npc)`
+All backface-culled except double-sided flowers → `Sprite.billboard(npc)` →
-→ `Framebuffer.quantize`. `chunkFar` is pure (camera + baked bounds + config
+the roaming mobs (each: shared local mesh × its `Mat4.compose` model matrix,
+double-sided) → `Framebuffer.quantize`. `chunkFar` is pure (camera + baked bounds + config
 only), so every worker band picks the same LOD for a chunk → no horizontal seam.
 Multi-threaded: N workers each run `renderBand` over
 their band of the shared framebuffer in parallel; single-threaded: one call over
@@ -306,6 +326,7 @@ job tmp dir, not the repo.
 ## Roadmap / not yet built
 
 In-browser RenderConfig slider panel; mipmaps; `painter` depth mode; gouraud
-lighting; more cloud types; more props / a weapon / moving enemies. `shared/`
+lighting; more cloud types; more props / a weapon; more mob kinds + smarter mob
+behavior (they wander + block/stand-on today, but don't yet react to the player). `shared/`
 is nearly empty. The FPS meter is static HTML + `textContent` writes only — no
 DOM-built UI yet (deliberate).

README.md

@@ -1,4 +1,7 @@
 # MEAT
 
 - knobs
-- toggle clouds: off, basic, fancy
+  - toggle clouds: off, basic, fancy
+  - all the knobs
+
+

app/assets.ts

@@ -1,8 +1,10 @@
 import type { Texture } from "../engine/render/Texture"
 import barkUrl from "../assets/bark.png"
+import beeUrl from "../assets/bee.png"
 import crateUrl from "../assets/crate.png"
 import floorUrl from "../assets/floor.png"
 import flowerUrl from "../assets/flower.png"
+import frogUrl from "../assets/frog.png"
 import grassUrl from "../assets/grass.png"
 import leafUrl from "../assets/leaf.png"
 import needleUrl from "../assets/needle.png"
@@ -21,11 +23,13 @@ export type Textures = {
   wall: Texture
   crate: Texture
   npc: Texture
+  frog: Texture
+  bee: Texture
 }
 
 /** Load every game texture up front. Call once before starting the loop. */
 export async function loadTextures(): Promise<Textures> {
-  const [floor, grass, bark, leaf, needle, rock, flower, wall, crate, npc] = await Promise.all([
+  const [floor, grass, bark, leaf, needle, rock, flower, wall, crate, npc, frog, bee] = await Promise.all([
     loadTexture(floorUrl),
     loadTexture(grassUrl),
     loadTexture(barkUrl),
@@ -36,8 +40,10 @@ export async function loadTextures(): Promise<Textures> {
     loadTexture(wallUrl),
     loadTexture(crateUrl),
     loadTexture(npcUrl),
+    loadTexture(frogUrl),
+    loadTexture(beeUrl),
   ])
-  return { floor, grass, bark, leaf, needle, rock, flower, wall, crate, npc }
+  return { floor, grass, bark, leaf, needle, rock, flower, wall, crate, npc, frog, bee }
 }
 
 function loadTexture(url: string): Promise<Texture> {

app/level.ts

@@ -4,6 +4,7 @@ import { STRIDE, type Mesh } from "../engine/scene/Mesh"
 import { Boulder } from "../engine/scene/Boulder"
 import { Bush } from "../engine/scene/Bush"
 import { Flower, type FlowerColor } from "../engine/scene/Flower"
+import type { Mob, MobKind } from "../engine/scene/Mob"
 import { Terrain } from "../engine/scene/Terrain"
 import { Tree } from "../engine/scene/Tree"
 
@@ -58,6 +59,9 @@ export type Level = {
   chunks: Chunk[]
   colliders: Aabb[]
   npcPosition: { x: number; y: number; z: number }
+  /** Roaming mobs -- simulated on the main thread each frame (see main.ts), not
+   *  baked into the static culled chunks. */
+  mobs: Mob[]
   terrain: Terrain
   sky: SkyConfig
 }
@@ -112,6 +116,14 @@ const FLOWER_SEED = 0xF10E
 const FLOWER_REACH = 0.3
 const FLOWER_COLORS: FlowerColor[] = ["white", "red", "yellow"]
 
+/** Roaming mobs: how many frogs/bees to scatter, their seed, and how far out they
+ *  reach (fraction of the world). Kept modest -- roaming meshes are drawn every
+ *  frame (frustum-culled), not baked into the static chunks. */
+const FROG_COUNT = 40
+const BEE_COUNT = 30
+const MOB_SEED = 0x30B
+const MOB_REACH = 0.5
+
 /** Spatial partition of the world for frustum culling: `CHUNK_GRID` x
  *  `CHUNK_GRID` square cells over [-outer, outer]. Smaller cells cull tighter
  *  (less drawn off-screen) but cost more per-cell tests + bounds; this is the
@@ -199,8 +211,9 @@ export function buildLevel(): Level {
   const bushes = placeBushes()
   const flowers = placeFlowers()
   const chunks = buildChunks(trees, boulders, bushes, flowers)
+  const mobs = placeMobs()
 
-  return { floor, walls, crate, chunks, colliders, npcPosition, terrain: TERRAIN, sky }
+  return { floor, walls, crate, chunks, colliders, npcPosition, mobs, terrain: TERRAIN, sky }
 }
 
 /** Bake the terrain + props into a `CHUNK_GRID` x `CHUNK_GRID` set of spatial
@@ -383,6 +396,43 @@ function placeFlowers(): Flower[] {
   return flowers
 }
 
+/** Scatter frogs + bees across the grass (like the boulders), each at its home
+ *  anchor with a random heading and size. No colliders here -- mobs move, so their
+ *  block/stand-on AABBs are rebuilt per frame in `main`. */
+function placeMobs(): Mob[] {
+  const rand = mulberry(MOB_SEED)
+  const maxDist = TERRAIN.outer * MOB_REACH
+  const mobs: Mob[] = []
+  const total = FROG_COUNT + BEE_COUNT
+  for (let guard = 0; mobs.length < total && guard < total * 20; guard++) {
+    const angle = rand() * Math.PI * 2
+    const dist = ARENA + 3 + rand() * (maxDist - ARENA - 3)
+    const x = Math.cos(angle) * dist
+    const z = Math.sin(angle) * dist
+    if (Math.max(Math.abs(x), Math.abs(z)) < TERRAIN.inner + 2) {
+      continue
+    }
+    const kind: MobKind = mobs.length < FROG_COUNT ? "frog" : "bee"
+    const y = Terrain.height(TERRAIN, x, z)
+    const scale = kind === "frog" ? 0.5 + rand() * 0.35 : 0.5 + rand() * 0.3
+    mobs.push({
+      kind,
+      home: { x, y, z },
+      position: { x, y, z },
+      heading: rand() * Math.PI * 2,
+      scale,
+      seed: (rand() * 0xFFFFFFFF) | 0,
+      vx: 0,
+      vz: 0,
+      vy: 0,
+      timer: rand() * 1.5,
+      phase: rand() * 10,
+      grounded: true,
+    })
+  }
+  return mobs
+}
+
 /** Deterministic 0..1 generator (mulberry32) for tree placement. */
 function mulberry(seed: number): () => number {
   let a = seed >>> 0

app/main.ts

@@ -1,12 +1,19 @@
 import { RenderConfig } from "../engine/render/RenderConfig"
 import { Camera } from "../engine/scene/Camera"
+import type { Mesh } from "../engine/scene/Mesh"
+import { Mob } from "../engine/scene/Mob"
+import type { Vec3 } from "../engine/math/Vec3"
 import { loadTextures } from "./assets"
-import { buildLevel } from "./level"
+import { buildLevel, type Level } from "./level"
 import { EYE_HEIGHT, Player } from "./player"
 import { createRenderer } from "./renderer"
-import { chunkFar, visibleChunks, type Scene } from "./renderScene"
+import { chunkFar, visibleChunks, visibleMobs, type Scene } from "./renderScene"
 
 const FOV = Math.PI / 3
+/** How close (world units) a mob must be to the player to get a live collider.
+ *  Mobs farther than this can't be touched this frame, so skip them -- keeps the
+ *  per-frame collider list (and the player's collision loop) short. */
+const MOB_COLLIDE_RANGE = 3
 
 const screen = document.querySelector<HTMLCanvasElement>("#screen")!
 const ctx = screen.getContext("2d")!
@@ -40,12 +47,20 @@ function benchStats(a: number[]): { median: number; p95: number; max: number; me
 async function main(): Promise<void> {
   const textures = await loadTextures()
   const level = buildLevel()
+  // Two canonical mob meshes, built once and shared by every instance (the sim
+  // supplies each mob's per-frame transform).
+  const frogMesh: Mesh = { verts: [], indices: [] }
+  const beeMesh: Mesh = { verts: [], indices: [] }
+  Mob.build("frog", frogMesh)
+  Mob.build("bee", beeMesh)
   const scene: Scene = {
     chunks: level.chunks,
     floor: level.floor,
     walls: level.walls,
     crate: level.crate,
     npc: { position: level.npcPosition, size: { x: 1.1, y: 1.5 } },
+    mobMesh: { frog: frogMesh, bee: beeMesh },
+    mobCount: level.mobs.length,
     sky: level.sky,
     textures,
   }
@@ -99,11 +114,13 @@ async function main(): Promise<void> {
   globalThis.addEventListener("resize", layout)
 
   if (benchMode) {
-    runBench(renderer, level.chunks, present, benchMode)
+    runBench(renderer, level, present, benchMode)
     return
   }
 
   const player: Player = { position: { x: 0, y: 0, z: 8 }, yaw: 0, pitch: 0, velocityY: 0, onGround: true }
+  // Colliders past this index are the dynamic mob ones, rebuilt every frame.
+  const staticColliderCount = level.colliders.length
   const keys = new Set<string>()
   globalThis.addEventListener("keydown", (e) => {
     keys.add(e.code)
@@ -200,6 +217,10 @@ async function main(): Promise<void> {
       presentMax = 0
       vsyncMax = 0
     }
+    for (const m of level.mobs) {
+      Mob.update(m, dt, level.terrain)
+    }
+    rebuildMobColliders(level, player.position, staticColliderCount)
     Player.update(player, keys, dt, level)
     const camera: Camera = {
       position: { x: player.position.x, y: player.position.y + EYE_HEIGHT, z: player.position.z },
@@ -209,9 +230,10 @@ async function main(): Promise<void> {
     }
     const viewProj = Camera.viewProjection(camera, renderer.fb.width / renderer.fb.height)
     const visible = visibleChunks(level.chunks, viewProj)
+    const mobDraws = visibleMobs(level.mobs, viewProj)
     lastVisible = visible
     lastCamera = camera
-    renderer.dispatch(camera, viewProj, visible, now / 1000)
+    renderer.dispatch(camera, viewProj, visible, now / 1000, mobDraws)
     inFlight = true
     if (renderer.done()) {
       show()
@@ -225,7 +247,7 @@ async function main(): Promise<void> {
  *  interval, then reports the distributions (exposed on `window.__BENCH__`). */
 function runBench(
   renderer: ReturnType<typeof createRenderer>,
-  chunks: Scene["chunks"],
+  level: Level,
   present: () => void,
   mode: string,
 ): void {
@@ -281,10 +303,14 @@ function runBench(
         return
       }
     }
+    for (const m of level.mobs) {
+      Mob.update(m, 1 / 60, level.terrain)
+    }
     const camera = benchCamera(i / 60)
     const viewProj = Camera.viewProjection(camera, renderer.fb.width / renderer.fb.height)
-    const visible = visibleChunks(chunks, viewProj)
+    const visible = visibleChunks(level.chunks, viewProj)
-    renderer.dispatch(camera, viewProj, visible, i / 60)
+    const mobDraws = visibleMobs(level.mobs, viewProj)
+    renderer.dispatch(camera, viewProj, visible, i / 60, mobDraws)
     inFlight = true
     if (renderer.done() && record()) {
       report()
@@ -293,6 +319,31 @@ function runBench(
   requestAnimationFrame(tick)
 }
 
+/** Rebuild the dynamic tail of `level.colliders`: keep the static prefix, then add
+ *  a block/stand-on AABB for each mob near the player. Mobs move, so these can't be
+ *  baked; frogs are `standable` (hop onto them), bees only block (no mid-air
+ *  platform). Only mobs within `MOB_COLLIDE_RANGE` are added -- the rest can't be
+ *  reached this frame anyway. */
+function rebuildMobColliders(level: Level, playerPos: Vec3, staticCount: number): void {
+  level.colliders.length = staticCount
+  for (const m of level.mobs) {
+    const dx = m.position.x - playerPos.x
+    const dz = m.position.z - playerPos.z
+    if (dx * dx + dz * dz > MOB_COLLIDE_RANGE * MOB_COLLIDE_RANGE) {
+      continue
+    }
+    const half = Mob.boundingRadius(m.kind) * m.scale * 0.7
+    level.colliders.push({
+      minX: m.position.x - half,
+      maxX: m.position.x + half,
+      minZ: m.position.z - half,
+      maxZ: m.position.z + half,
+      top: m.position.y + Mob.bodyHeight(m.kind) * m.scale,
+      standable: m.kind === "frog",
+    })
+  }
+}
+
 main().catch((error) => {
   console.error(error)
 })

app/render-worker.ts

@@ -1,6 +1,6 @@
 import type { Framebuffer } from "../engine/render/Framebuffer"
 import type { RenderConfig } from "../engine/render/RenderConfig"
-import { renderBand, type Scene } from "./renderScene"
+import { renderBand, MOB_FLOATS, type MobDraw, type Scene } from "./renderScene"
 
 /** One-time setup: shared framebuffer + control/param buffers, the (cloned)
  *  scene, this worker's row band, and its index into the per-worker times array. */
@@ -17,6 +17,7 @@ type Init = {
   camSAB: SharedArrayBuffer
   vpSAB: SharedArrayBuffer
   visSAB: SharedArrayBuffer
+  mobSAB: SharedArrayBuffer
   timesSAB: SharedArrayBuffer
   index: number
 }
@@ -24,6 +25,7 @@ type Init = {
 const FRAME = 0
 const DONE = 1
 const VIS = 2
+const MOBVIS = 3
 
 const ctx = globalThis as unknown as {
   addEventListener: (type: "message", handler: (e: { data: Init }) => void) => void
@@ -41,6 +43,7 @@ ctx.addEventListener("message", (e) => {
   const cam = new Float64Array(m.camSAB)
   const vp = new Float32Array(m.vpSAB)
   const vis = new Int32Array(m.visSAB)
+  const mob = new Float32Array(m.mobSAB)
   const times = new Float64Array(m.timesSAB)
   const { scene, band, config, skyStep, index } = m
 
@@ -54,7 +57,13 @@ ctx.addEventListener("message", (e) => {
     const camera = { position: { x: cam[0], y: cam[1], z: cam[2] }, yaw: cam[3], pitch: cam[4], fov: cam[5] }
     const count = Atomics.load(ctrl, VIS)
     const visible = [...vis.subarray(0, count)]
-    renderBand(fb, scene, camera, vp, visible, config, skyStep, cam[6], band[0], band[1])
+    const mobCount = Atomics.load(ctrl, MOBVIS)
+    const mobDraws: MobDraw[] = []
+    for (let i = 0; i < mobCount; i++) {
+      const o = i * MOB_FLOATS
+      mobDraws.push({ kind: mob[o] === 1 ? "bee" : "frog", x: mob[o + 1], y: mob[o + 2], z: mob[o + 3], heading: mob[o + 4], scale: mob[o + 5] })
+    }
+    renderBand(fb, scene, camera, vp, visible, mobDraws, config, skyStep, cam[6], band[0], band[1])
     times[index] = performance.now() - t0
     Atomics.add(ctrl, DONE, 1)
   }

app/renderScene.ts

@@ -4,8 +4,9 @@ import { Rasterizer } from "../engine/render/Rasterizer"
 import type { RenderConfig } from "../engine/render/RenderConfig"
 import { Sky, type SkyConfig } from "../engine/render/Sky"
 import type { Camera } from "../engine/scene/Camera"
-import type { Mat4 } from "../engine/math/Mat4"
+import { Mat4 } from "../engine/math/Mat4"
 import type { Mesh } from "../engine/scene/Mesh"
+import { Mob, type MobKind } from "../engine/scene/Mob"
 import { Sprite } from "../engine/scene/Sprite"
 import type { Vec2 } from "../engine/math/Vec2"
 import type { Vec3 } from "../engine/math/Vec3"
@@ -21,10 +22,22 @@ export type Scene = {
   walls: Mesh
   crate: Mesh
   npc: { position: Vec3; size: Vec2 }
+  /** Canonical local-space mob meshes, one per kind, built once + shared by every
+   *  instance (each instance differs only by its per-frame model matrix). */
+  mobMesh: { frog: Mesh; bee: Mesh }
+  /** How many mobs the sim has -- sizes the worker's shared transform buffer. */
+  mobCount: number
   sky: SkyConfig
   textures: Textures
 }
 
+/** One mob's live transform for a frame: which mesh + where/how to place it.
+ *  Produced by `visibleMobs` on the main thread, then either passed straight to
+ *  `renderBand` (single-thread) or packed into the shared `mobState` buffer and
+ *  rebuilt in each worker. `MOB_FLOATS` is that packed layout's stride. */
+export type MobDraw = { kind: MobKind; x: number; y: number; z: number; heading: number; scale: number }
+export const MOB_FLOATS = 6 // kind(0/1), x, y, z, heading, scale
+
 /** Chunk indices whose bounding box is inside the view frustum. Computed once on
  *  the main thread and shared with every worker (so they don't each re-cull). */
 export function visibleChunks(chunks: Chunk[], viewProj: Mat4): number[] {
@@ -39,6 +52,24 @@ export function visibleChunks(chunks: Chunk[], viewProj: Mat4): number[] {
   return out
 }
 
+/** The `MobDraw`s for mobs whose world AABB is inside the view frustum. Mobs move,
+ *  so (unlike chunks) they can't be baked into the culled world -- they're culled
+ *  here per frame instead. Computed once on the main thread; the visible set is
+ *  what gets shipped to the workers. */
+export function visibleMobs(mobs: Mob[], viewProj: Mat4): MobDraw[] {
+  const frustum = Frustum.fromViewProj(viewProj)
+  const out: MobDraw[] = []
+  for (const m of mobs) {
+    const r = Mob.boundingRadius(m.kind) * m.scale
+    const h = Mob.bodyHeight(m.kind) * m.scale
+    const p = m.position
+    if (Frustum.intersectsAabb(frustum, p.x - r, p.y - r, p.z - r, p.x + r, p.y + h + r, p.z + r)) {
+      out.push({ kind: m.kind, x: p.x, y: p.y, z: p.z, heading: m.heading, scale: m.scale })
+    }
+  }
+  return out
+}
+
 /**
  * Render rows [y0, y1) of one frame into `fb`. This is the single source of
  * render truth: the single-thread path calls it with the full height, and each
@@ -51,6 +82,7 @@ export function renderBand(
   camera: Camera,
   viewProj: Mat4,
   visible: number[],
+  mobDraws: MobDraw[],
   config: RenderConfig,
   skyStep: number,
   time: number,
@@ -84,6 +116,15 @@ export function renderBand(
   }
   const sprite: Sprite = { position: scene.npc.position, size: scene.npc.size, texture: tx.npc }
   Rasterizer.draw(fb, Sprite.billboard(sprite, camera), tx.npc, viewProj, config, false, y0, y1)
+  // Roaming mobs: each is the shared local-space mesh for its kind, placed by its
+  // own model matrix (viewProj x model). Drawn double-sided (cull off) -- they're
+  // small and few, so the winding-correct backface cull isn't worth the fuss.
+  for (const m of mobDraws) {
+    const mesh = m.kind === "bee" ? scene.mobMesh.bee : scene.mobMesh.frog
+    const texture = m.kind === "bee" ? tx.bee : tx.frog
+    const mvp = Mat4.multiply(viewProj, Mat4.compose(m.x, m.y, m.z, m.heading, m.scale))
+    Rasterizer.draw(fb, mesh, texture, mvp, config, false, y0, y1)
+  }
   Framebuffer.quantize(fb, config, y0, y1)
 }
 

app/renderer.ts

@@ -2,7 +2,7 @@ import { Framebuffer } from "../engine/render/Framebuffer"
 import type { RenderConfig } from "../engine/render/RenderConfig"
 import type { Mat4 } from "../engine/math/Mat4"
 import type { Camera } from "../engine/scene/Camera"
-import { renderBand, type Scene } from "./renderScene"
+import { renderBand, MOB_FLOATS, type MobDraw, type Scene } from "./renderScene"
 
 /** Sky is drawn at 1/SKY_STEP resolution; band splits align to it. */
 const SKY_STEP = 2
@@ -21,6 +21,7 @@ const MAX_WORKERS = 3
 const FRAME = 0 // bumped by main to dispatch a frame
 const DONE = 1 // workers add 1 when their band is finished
 const VIS = 2 // number of visible chunk indices this frame
+const MOBVIS = 3 // number of visible mobs this frame
 
 /**
  * Render driver. When the page is cross-origin-isolated it runs a pool of worker
@@ -38,7 +39,7 @@ export type Renderer = {
   readonly parallel: boolean
   reconfigure: (config: RenderConfig) => void
   /** Start rendering one frame (non-blocking in the worker path). */
-  dispatch: (camera: Camera, viewProj: Mat4, visible: number[], time: number) => void
+  dispatch: (camera: Camera, viewProj: Mat4, visible: number[], time: number, mobDraws: MobDraw[]) => void
   /** Has the dispatched frame finished? (always true single-threaded.) */
   done: () => boolean
   /** Critical-path render time of the last frame, ms (max band time / inline time). */
@@ -49,6 +50,7 @@ export function createRenderer(scene: Scene, initial: RenderConfig, forceWorkers
   const hw = (globalThis.navigator as Navigator | undefined)?.hardwareConcurrency ?? 4
   const workerCount = Math.max(1, Math.min(MAX_WORKERS, hw - 1))
   const maxVis = Math.max(1, scene.chunks.length)
+  const maxMobs = Math.max(1, scene.mobCount)
   let config = initial
   const want = forceWorkers ?? ENABLE_WORKERS
   let parallel = want && canShare()
@@ -59,6 +61,7 @@ export function createRenderer(scene: Scene, initial: RenderConfig, forceWorkers
   let cam: Float64Array<ArrayBufferLike> = new Float64Array(0) // pos x/y/z, yaw, pitch, fov, time
   let vp: Float32Array<ArrayBufferLike> = new Float32Array(0) // the view-projection matrix
   let vis: Int32Array<ArrayBufferLike> = new Int32Array(0) // visible chunk indices
+  let mob: Float32Array<ArrayBufferLike> = new Float32Array(0) // visible mob transforms (MOB_FLOATS each)
   let times: Float64Array<ArrayBufferLike> = new Float64Array(0) // per-worker band render ms
   let lastWork = 0
 
@@ -77,6 +80,7 @@ export function createRenderer(scene: Scene, initial: RenderConfig, forceWorkers
       cam = new Float64Array(new SharedArrayBuffer(7 * 8))
       vp = new Float32Array(new SharedArrayBuffer(16 * 4))
       vis = new Int32Array(new SharedArrayBuffer(maxVis * 4))
+      mob = new Float32Array(new SharedArrayBuffer(maxMobs * MOB_FLOATS * 4))
       times = new Float64Array(new SharedArrayBuffer(bands.length * 8))
       try {
         bands.forEach((band, index) => {
@@ -97,6 +101,7 @@ export function createRenderer(scene: Scene, initial: RenderConfig, forceWorkers
             camSAB: cam.buffer,
             vpSAB: vp.buffer,
             visSAB: vis.buffer,
+            mobSAB: mob.buffer,
             timesSAB: times.buffer,
             index,
           })
@@ -127,7 +132,7 @@ export function createRenderer(scene: Scene, initial: RenderConfig, forceWorkers
       config = next
       setup()
     },
-    dispatch(camera, viewProj, visible, time) {
+    dispatch(camera, viewProj, visible, time, mobDraws) {
       if (parallel && workers.length > 0) {
         cam[0] = camera.position.x
         cam[1] = camera.position.y
@@ -141,14 +146,26 @@ export function createRenderer(scene: Scene, initial: RenderConfig, forceWorkers
         for (let i = 0; i < count; i++) {
           vis[i] = visible[i]
         }
+        const mobCount = Math.min(mobDraws.length, maxMobs)
+        for (let i = 0; i < mobCount; i++) {
+          const d = mobDraws[i]
+          const o = i * MOB_FLOATS
+          mob[o] = d.kind === "bee" ? 1 : 0
+          mob[o + 1] = d.x
+          mob[o + 2] = d.y
+          mob[o + 3] = d.z
+          mob[o + 4] = d.heading
+          mob[o + 5] = d.scale
+        }
         Atomics.store(ctrl, VIS, count)
+        Atomics.store(ctrl, MOBVIS, mobCount)
         Atomics.store(ctrl, DONE, 0)
         Atomics.add(ctrl, FRAME, 1)
         Atomics.notify(ctrl, FRAME, workers.length)
         return
       }
       const t0 = performance.now()
-      renderBand(fb, scene, camera, viewProj, visible, config, SKY_STEP, time, 0, fb.height)
+      renderBand(fb, scene, camera, viewProj, visible, mobDraws, config, SKY_STEP, time, 0, fb.height)
       lastWork = performance.now() - t0
     },
     done() {

engine/math/Mat4.ts

@@ -20,6 +20,26 @@ export namespace Mat4 {
     return out
   }
 
+  /** Model transform T * Ry * S: uniform `scale`, then a yaw rotation about Y,
+   *  then a translation. Built directly in column-major storage (no intermediate
+   *  matmuls) since it runs per mob per frame. A vertex at local +Z ends up
+   *  pointing along world (sin yaw, 0, cos yaw), i.e. the object faces `yaw`. */
+  export function compose(tx: number, ty: number, tz: number, yaw: number, scale: number): Mat4 {
+    const c = Math.cos(yaw)
+    const s = Math.sin(yaw)
+    const out = new Float32Array(16)
+    out[0] = scale * c
+    out[2] = scale * -s
+    out[5] = scale
+    out[8] = scale * s
+    out[10] = scale * c
+    out[12] = tx
+    out[13] = ty
+    out[14] = tz
+    out[15] = 1
+    return out
+  }
+
   /** Right-handed perspective projection (camera looks down -Z). Maps the view
    *  frustum to clip space; the -1 in row 3 copies -z into w, so the later
    *  divide by w is what produces foreshortening. */

engine/scene/Mob.ts

@@ -0,0 +1,264 @@
+import { Terrain } from "./Terrain"
+import type { Vec3 } from "../math/Vec3"
+import { STRIDE, type Mesh } from "./Mesh"
+
+const TAU = Math.PI * 2
+
+/** A roaming creature drawn as a moving low-poly mesh (unlike the static baked
+ *  world). Two kinds, told apart by silhouette + motion:
+ *   frog -- squat, ground-bound, sits then springs a ballistic hop.
+ *   bee  -- small, hovers and darts through the air, wings out.
+ *
+ *  Unlike `Tree`/`Boulder` (baked once into world-space chunks), a mob's geometry
+ *  is a **canonical local-space mesh** built once per kind (front = +Z, frog feet
+ *  / bee body at the origin); the live `position`/`heading`/`scale` are turned
+ *  into a per-frame model matrix by the renderer. All wander state lives here so
+ *  `update` is a pure stepping function of the mob + dt (deterministic via the
+ *  evolving `seed`), which keeps the sim on the main thread and cloneable-free. */
+export type MobKind = "frog" | "bee"
+
+export type Mob = {
+  kind: MobKind
+  /** Leash anchor (where it was scattered); wandering is pulled back toward it. */
+  home: Vec3
+  /** Live feet-center (frog) / body-center (bee), advanced each frame. */
+  position: Vec3
+  /** Facing yaw; the mesh's front is local +Z, so world dir = (sin h, 0, cos h). */
+  heading: number
+  /** Per-instance size multiplier. */
+  scale: number
+  /** Evolving RNG state (mutated by `update`) -- keeps the sim deterministic. */
+  seed: number
+  /** Horizontal velocity (frog: only mid-hop; bee: cruise). */
+  vx: number
+  vz: number
+  /** Vertical velocity (frog ballistic hop; bee stays 0, it uses a bob). */
+  vy: number
+  /** Countdown to the next decision (frog: next hop; bee: next heading change). */
+  timer: number
+  /** Accumulated time, for the bee's hover bob. */
+  phase: number
+  /** Frog only: resting on the ground vs airborne in a hop. */
+  grounded: boolean
+}
+
+// --- Behavior tuning ------------------------------------------------------
+const FROG_LEASH = 5
+const FROG_REST_MIN = 0.7
+const FROG_REST_SPAN = 1.8
+const FROG_HOP_SPEED = 1.6
+const FROG_HOP_IMPULSE = 3.2
+const FROG_GRAVITY = 14
+const BEE_LEASH = 6
+const BEE_SPEED = 1.7
+const BEE_TURN_MIN = 0.4
+const BEE_TURN_SPAN = 1
+const BEE_HOVER = 1.1
+const BEE_BOB_AMP = 0.18
+const BEE_BOB_FREQ = 3
+
+export namespace Mob {
+  /** Advance one mob by `dt` seconds, sampling `terrain` for ground height. */
+  export function update(mob: Mob, dt: number, terrain: Terrain): void {
+    if (mob.kind === "frog") {
+      frog(mob, dt, terrain)
+    } else {
+      bee(mob, dt, terrain)
+    }
+  }
+
+  /** Append the canonical local-space mesh for `kind` into `mesh` (called once
+   *  per kind at load; every instance shares it, differing only by transform). */
+  export function build(kind: MobKind, mesh: Mesh): void {
+    if (kind === "frog") {
+      buildFrog(mesh)
+    } else {
+      buildBee(mesh)
+    }
+  }
+
+  /** Local bounding radius (pre-scale), for building the per-frame cull AABB. */
+  export function boundingRadius(kind: MobKind): number {
+    return kind === "frog" ? 0.7 : 0.5
+  }
+
+  /** Local body height (pre-scale), for the top of the stand-on collider. */
+  export function bodyHeight(kind: MobKind): number {
+    return kind === "frog" ? 0.6 : 0.5
+  }
+
+  // --- Simulation ---------------------------------------------------------
+
+  function frog(mob: Mob, dt: number, terrain: Terrain): void {
+    if (mob.grounded) {
+      mob.timer -= dt
+      mob.position.y = Terrain.height(terrain, mob.position.x, mob.position.z)
+      if (mob.timer > 0) {
+        return
+      }
+      // Launch a hop: pick a heading (pulled homeward past the leash), then
+      // convert it into a forward+upward ballistic velocity.
+      mob.heading = wanderHeading(mob, FROG_LEASH, 0.9)
+      mob.vx = Math.sin(mob.heading) * FROG_HOP_SPEED
+      mob.vz = Math.cos(mob.heading) * FROG_HOP_SPEED
+      mob.vy = FROG_HOP_IMPULSE
+      mob.grounded = false
+      return
+    }
+    mob.vy -= FROG_GRAVITY * dt
+    mob.position.x += mob.vx * dt
+    mob.position.y += mob.vy * dt
+    mob.position.z += mob.vz * dt
+    const ground = Terrain.height(terrain, mob.position.x, mob.position.z)
+    if (mob.position.y <= ground && mob.vy < 0) {
+      mob.position.y = ground
+      mob.vx = 0
+      mob.vy = 0
+      mob.vz = 0
+      mob.grounded = true
+      mob.timer = FROG_REST_MIN + nextRand(mob) * FROG_REST_SPAN
+    }
+  }
+
+  function bee(mob: Mob, dt: number, terrain: Terrain): void {
+    mob.phase += dt
+    mob.timer -= dt
+    if (mob.timer <= 0) {
+      mob.heading = wanderHeading(mob, BEE_LEASH, 1.4)
+      mob.timer = BEE_TURN_MIN + nextRand(mob) * BEE_TURN_SPAN
+    }
+    mob.position.x += Math.sin(mob.heading) * BEE_SPEED * dt
+    mob.position.z += Math.cos(mob.heading) * BEE_SPEED * dt
+    const ground = Terrain.height(terrain, mob.position.x, mob.position.z)
+    mob.position.y = ground + BEE_HOVER + Math.sin(mob.phase * BEE_BOB_FREQ) * BEE_BOB_AMP
+  }
+
+  /** A new heading: free wander when inside the leash, else biased back toward
+   *  home so the mob never drifts off into the peaks (`jitter` = the random cone
+   *  half-width in radians layered on top of the homeward bearing). */
+  function wanderHeading(mob: Mob, leash: number, jitter: number): number {
+    const dx = mob.home.x - mob.position.x
+    const dz = mob.home.z - mob.position.z
+    if (dx * dx + dz * dz > leash * leash) {
+      return Math.atan2(dx, dz) + (nextRand(mob) - 0.5) * jitter
+    }
+    return nextRand(mob) * TAU
+  }
+
+  /** mulberry32 step over the mob's own `seed` (mutated), so a mob's motion is
+   *  deterministic and needs no external RNG object to clone. */
+  function nextRand(mob: Mob): number {
+    const a = (mob.seed + 0x6D2B79F5) | 0
+    mob.seed = a
+    let t = Math.imul(a ^ (a >>> 15), 1 | a)
+    t ^= t + Math.imul(t ^ (t >>> 7), 61 | t)
+    return ((t ^ (t >>> 14)) >>> 0) / 4294967296
+  }
+
+  // --- Geometry -----------------------------------------------------------
+  // Mobs are drawn double-sided (see renderScene), so winding is not load-bearing
+  // here -- these builders only need to place faceted, flat-shaded surfaces.
+
+  function buildFrog(mesh: Mesh): void {
+    // Wide squat body, two eye bumps on the top-front, two hind haunches. UVs:
+    // the frog texture is green skin on the left, a dark eye tone on the right.
+    ellipsoid(mesh, 0, 0.26, 0, 0.5, 0.28, 0.52, 6, 4, 0, 0.68, 0, 1)
+    ellipsoid(mesh, 0.24, 0.5, 0.26, 0.13, 0.13, 0.13, 4, 3, 0.75, 0.98, 0, 1)
+    ellipsoid(mesh, -0.24, 0.5, 0.26, 0.13, 0.13, 0.13, 4, 3, 0.75, 0.98, 0, 1)
+    ellipsoid(mesh, 0.3, 0.2, -0.26, 0.2, 0.2, 0.26, 4, 3, 0, 0.68, 0, 1)
+    ellipsoid(mesh, -0.3, 0.2, -0.26, 0.2, 0.2, 0.26, 4, 3, 0, 0.68, 0, 1)
+  }
+
+  function buildBee(mesh: Mesh): void {
+    // Fore-aft ovoid body striped along its length, a dark head at the front, two
+    // pale wings. UVs: bee texture is stripe bands (left), head-dark (mid), wing-
+    // pale (right); the body maps v along z so the stripes band across it.
+    ovoidZ(mesh, -0.4, 0.4, 0.24, 7, 5, 0, 0.54, 0, 1)
+    ellipsoid(mesh, 0, 0.02, 0.44, 0.16, 0.16, 0.16, 5, 4, 0.6, 0.79, 0, 1)
+    wing(mesh, 1, 0.83, 0.99, 0, 1)
+    wing(mesh, -1, 0.83, 0.99, 0, 1)
+  }
+
+  /** A UV-rected ellipsoid (pole on Y), faceted like the boulders. */
+  function ellipsoid(
+    mesh: Mesh,
+    cx: number,
+    cy: number,
+    cz: number,
+    rx: number,
+    ry: number,
+    rz: number,
+    seg: number,
+    rings: number,
+    u0: number,
+    u1: number,
+    v0: number,
+    v1: number,
+  ): void {
+    const start = mesh.verts.length / STRIDE
+    for (let ir = 0; ir <= rings; ir++) {
+      const phi = (ir / rings) * Math.PI
+      const cyv = Math.cos(phi)
+      const crv = Math.sin(phi)
+      const v = v0 + (v1 - v0) * (ir / rings)
+      for (let is = 0; is <= seg; is++) {
+        const theta = (is / seg) * TAU
+        const u = u0 + (u1 - u0) * (is / seg)
+        mesh.verts.push(cx + crv * Math.cos(theta) * rx, cy + cyv * ry, cz + crv * Math.sin(theta) * rz, u, v)
+      }
+    }
+    quadGrid(mesh, start, seg, rings)
+  }
+
+  /** An ovoid whose pole axis is Z (rings step along z, tapering at both ends),
+   *  so the mapped `v` runs down the body's length -- used for the bee's stripes. */
+  function ovoidZ(
+    mesh: Mesh,
+    z0: number,
+    z1: number,
+    r: number,
+    seg: number,
+    rings: number,
+    u0: number,
+    u1: number,
+    v0: number,
+    v1: number,
+  ): void {
+    const start = mesh.verts.length / STRIDE
+    for (let ir = 0; ir <= rings; ir++) {
+      const t = ir / rings
+      const z = z0 + (z1 - z0) * t
+      const rr = r * (0.15 + 0.85 * Math.sin(t * Math.PI))
+      const v = v0 + (v1 - v0) * t
+      for (let is = 0; is <= seg; is++) {
+        const theta = (is / seg) * TAU
+        const u = u0 + (u1 - u0) * (is / seg)
+        mesh.verts.push(Math.cos(theta) * rr, Math.sin(theta) * rr, z, u, v)
+      }
+    }
+    quadGrid(mesh, start, seg, rings)
+  }
+
+  /** Index a (seg x rings) vertex grid (row = seg+1) into two tris per cell. */
+  function quadGrid(mesh: Mesh, start: number, seg: number, rings: number): void {
+    const row = seg + 1
+    for (let ir = 0; ir < rings; ir++) {
+      for (let is = 0; is < seg; is++) {
+        const p = start + ir * row + is
+        mesh.indices.push(p, p + 1, p + row + 1, p, p + row + 1, p + row)
+      }
+    }
+  }
+
+  /** One flat wing quad on `side` (+1 right / -1 left), swept up and out. */
+  function wing(mesh: Mesh, side: number, u0: number, u1: number, v0: number, v1: number): void {
+    const base = mesh.verts.length / STRIDE
+    mesh.verts.push(
+      side * 0.06, 0.12, 0.14, u0, v0,
+      side * 0.42, 0.24, 0.1, u1, v0,
+      side * 0.42, 0.24, -0.12, u1, v1,
+      side * 0.06, 0.12, -0.1, u0, v1,
+    )
+    mesh.indices.push(base, base + 1, base + 2, base, base + 2, base + 3)
+  }
+}

scripts/gen-assets.ts

@@ -194,6 +194,31 @@ const crate: Shade = (x, y) => {
   return [140 + n, 96 + n, 46 + n, 255]
 }
 
+// Frog skin atlas: green mottled skin with a lighter belly on the left (u<0.71),
+// a dark eye tone on the right (mapped by the eye/haunch bumps' UVs).
+const frog: Shade = (x, y) => {
+  const n = noise(x, y) * 10
+  if (x < 34) {
+    const belly = (y / 48) * 28
+    return [66 + n, 120 + belly + n, 60 + n, 255]
+  }
+  return [26 + n, 42 + n, 30 + n, 255]
+}
+
+// Bee atlas: yellow/black stripe bands down the left (u<0.54, banded by y so the
+// body stripes across its length), a dark head tone in the middle, pale wings on
+// the right.
+const bee: Shade = (x, y) => {
+  const n = noise(x, y) * 8
+  if (x < 26) {
+    return Math.floor(y / 6) % 2 === 0 ? [250 + n, 206 + n, 42 + n, 255] : [30 + n, 26 + n, 14 + n, 255]
+  }
+  if (x < 38) {
+    return [36 + n, 30 + n, 18 + n, 255]
+  }
+  return [228 + n, 238 + n, 248 + n, 255]
+}
+
 // 48x64, transparent background, a simple round-topped figure with eyes.
 const npc: Shade = (x, y) => {
   const dx = (x - 24) / 17
@@ -231,6 +256,8 @@ const assets: Array<[string, number, number, Shade]> = [
   ["wall", 64, 64, wall],
   ["crate", 64, 64, crate],
   ["npc", 48, 64, npc],
+  ["frog", 48, 48, frog],
+  ["bee", 48, 48, bee],
 ]
 
 for (const [name, w, h, shade] of assets) {