diff --git a/frontend/apps/artcraft-website-next/TUNER.md b/frontend/apps/artcraft-website-next/TUNER.md
new file mode 100644
index 0000000000..8f93e11bce
--- /dev/null
+++ b/frontend/apps/artcraft-website-next/TUNER.md
@@ -0,0 +1,61 @@
+# Dev Tuner
+
+A floating, draggable panel for live-tuning the site's visual/physics
+constants without an edit-build-reload loop. Drag it by its header; collapse
+the whole box with `–`, or expand/collapse individual sections.
+
+## When it shows
+
+- Always in `next dev`.
+- In any build when the URL has `?tuner=1` (handy for tuning a deployed
+  preview).
+- Never otherwise — production visitors don't see it.
+
+## Behavior
+
+- **Live**: physics/lighting/material values are read every frame, so slider
+  changes apply instantly. Formation values (anything that changes the ball
+  arrangement itself) trigger a debounced rebuild (~250 ms after the last
+  change).
+- **Persistent**: tuned values are stored in `localStorage`
+  (`artcraft-tuner`), so a refresh keeps your tuning. Panel position and
+  section collapse state persist too (`artcraft-tuner-ui`).
+- **Modified values** show their label in the accent color.
+- **Copy** puts a JSON snapshot of all current values on the clipboard —
+  paste it into a message or use it to update defaults in code.
+- **Reset** clears every override back to the in-code defaults.
+
+## Adding tunables (POLICY: always do this)
+
+Whenever you introduce a new tweakable constant — a force, an intensity, a
+size, a duration — register it with the tuner instead of hardcoding a bare
+literal. Adding a slider is free; a missing one costs a whole
+iteration/build round-trip.
+
+```ts
+// some-feature-tunables.ts
+import { defineTunables } from "@/lib/tuner";
+
+export const glowTuner = defineTunables("glow", "Glow", {
+  radius: { label: "Radius px", min: 0, max: 400, step: 5, default: 120 },
+  strength: { label: "Strength", min: 0, max: 2, step: 0.05, default: 0.8 },
+});
+```
+
+Then read values where they're used:
+
+- **Per-frame consumers** (`useFrame`, rAF loops): call `glowTuner.read()`
+  inside the loop — it's cheap and picks up changes instantly.
+- **Build-time consumers** (values baked into geometry/sampling): read at
+  build time and subscribe to `useTunerStore` to trigger a debounced rebuild
+  when the group's values change (see the Formation wiring in
+  `hero-wordmark.tsx`).
+
+The panel picks up new groups automatically — no panel changes needed.
+Registered groups: Formation, Physics, Cursor & Light, Material, Halo (all
+for the hero wordmark; see `src/components/landing/hero-tunables.ts`).
+
+## Shipping tuned values
+
+The defaults in `defineTunables` are the shipped values. After a tuning
+session: Copy → paste the JSON → update the `default:` fields → Reset.
diff --git a/frontend/apps/artcraft-website-next/src/app/layout.tsx b/frontend/apps/artcraft-website-next/src/app/layout.tsx
index 788cca8de8..7282200d44 100644
--- a/frontend/apps/artcraft-website-next/src/app/layout.tsx
+++ b/frontend/apps/artcraft-website-next/src/app/layout.tsx
@@ -3,6 +3,7 @@ import { Outfit, Instrument_Serif, Source_Sans_3, Geist_Mono } from "next/font/g
 import SiteNav from "@/components/site-nav";
 import SiteFooter from "@/components/site-footer";
 import MotionProvider from "@/components/motion-provider";
+import TunerPanel from "@/components/dev/tuner-panel";
 import "./globals.css";
 
 const SITE_URL = "https://getartcraft.com";
@@ -103,6 +104,7 @@ export default function RootLayout({
           <main>{children}</main>
           <SiteFooter />
         </MotionProvider>
+        <TunerPanel />
       </body>
     </html>
   );
diff --git a/frontend/apps/artcraft-website-next/src/components/dev/tuner-panel.tsx b/frontend/apps/artcraft-website-next/src/components/dev/tuner-panel.tsx
new file mode 100644
index 0000000000..cbc323c2d1
--- /dev/null
+++ b/frontend/apps/artcraft-website-next/src/components/dev/tuner-panel.tsx
@@ -0,0 +1,237 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+import {
+  useTunerStore,
+  tunerSnapshot,
+  type TunableGroup,
+} from "@/lib/tuner";
+
+const UI_KEY = "artcraft-tuner-ui";
+
+type UiState = {
+  x: number;
+  y: number;
+  collapsed: boolean;
+  open: Record<string, boolean>;
+};
+
+const DEFAULT_UI: UiState = { x: 16, y: 72, collapsed: false, open: {} };
+
+function loadUi(): UiState {
+  try {
+    return { ...DEFAULT_UI, ...JSON.parse(localStorage.getItem(UI_KEY) ?? "{}") };
+  } catch {
+    return DEFAULT_UI;
+  }
+}
+
+// Floating dev tuner: renders every group registered via defineTunables as a
+// collapsible section of slider + number-input rows. Drag by the header.
+// Shown in dev builds, or anywhere with ?tuner=1. See TUNER.md.
+export default function TunerPanel() {
+  const [enabled, setEnabled] = useState(false);
+  useEffect(() => {
+    setEnabled(
+      process.env.NODE_ENV === "development" ||
+        new URLSearchParams(window.location.search).has("tuner"),
+    );
+  }, []);
+  if (!enabled) return null;
+  return <Panel />;
+}
+
+function Panel() {
+  const groups = useTunerStore((s) => s.groups);
+  const resetAll = useTunerStore((s) => s.resetAll);
+  const [ui, setUi] = useState<UiState>(loadUi);
+  const [copied, setCopied] = useState(false);
+  const dragOrigin = useRef<{ px: number; py: number; x: number; y: number } | null>(null);
+
+  const saveUi = (next: UiState) => {
+    setUi(next);
+    try {
+      localStorage.setItem(UI_KEY, JSON.stringify(next));
+    } catch {
+      // Non-persistent tuning is still tuning.
+    }
+  };
+
+  const onHeaderPointerDown = (e: React.PointerEvent) => {
+    (e.target as HTMLElement).setPointerCapture?.(e.pointerId);
+    dragOrigin.current = { px: e.clientX, py: e.clientY, x: ui.x, y: ui.y };
+  };
+  const onHeaderPointerMove = (e: React.PointerEvent) => {
+    const o = dragOrigin.current;
+    if (!o) return;
+    saveUi({
+      ...ui,
+      x: Math.max(0, Math.min(window.innerWidth - 60, o.x + e.clientX - o.px)),
+      y: Math.max(0, Math.min(window.innerHeight - 40, o.y + e.clientY - o.py)),
+    });
+  };
+  const onHeaderPointerUp = () => {
+    dragOrigin.current = null;
+  };
+
+  const copyValues = async () => {
+    try {
+      await navigator.clipboard.writeText(
+        JSON.stringify(tunerSnapshot(), null, 2),
+      );
+      setCopied(true);
+      setTimeout(() => setCopied(false), 1200);
+    } catch {
+      // Clipboard can be blocked; the values are still visible in the panel.
+    }
+  };
+
+  const ordered = Object.values(groups).sort((a, b) => a.order - b.order);
+
+  return (
+    <div
+      className="fixed z-[100] w-[300px] border border-line-strong bg-bg-raised text-ink shadow-[0_8px_32px_rgba(0,0,0,0.35)] select-none"
+      style={{ left: ui.x, top: ui.y }}
+    >
+      <div
+        className="flex cursor-grab items-center justify-between border-b border-line bg-bg-sunken px-3 py-2 active:cursor-grabbing"
+        onPointerDown={onHeaderPointerDown}
+        onPointerMove={onHeaderPointerMove}
+        onPointerUp={onHeaderPointerUp}
+      >
+        <p className="hud-label font-bold">Tuner</p>
+        <div className="flex items-center gap-1">
+          <HeaderButton onClick={copyValues} label={copied ? "Copied" : "Copy"} />
+          <HeaderButton onClick={resetAll} label="Reset" />
+          <HeaderButton
+            onClick={() => saveUi({ ...ui, collapsed: !ui.collapsed })}
+            label={ui.collapsed ? "+" : "–"}
+          />
+        </div>
+      </div>
+
+      {!ui.collapsed && (
+        <div className="max-h-[70vh] overflow-y-auto">
+          {ordered.length === 0 && (
+            <p className="hud-label px-3 py-4 text-faint">
+              No tunables registered
+            </p>
+          )}
+          {ordered.map((group) => (
+            <Section
+              key={group.id}
+              group={group}
+              open={ui.open[group.id] ?? false}
+              onToggle={() =>
+                saveUi({
+                  ...ui,
+                  open: { ...ui.open, [group.id]: !(ui.open[group.id] ?? false) },
+                })
+              }
+            />
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
+
+function HeaderButton({ onClick, label }: { onClick: () => void; label: string }) {
+  return (
+    <button
+      type="button"
+      onClick={onClick}
+      onPointerDown={(e) => e.stopPropagation()}
+      className="hud-label min-w-[44px] border border-line px-1.5 py-0.5 text-[10px] text-muted hover:bg-invert-bg hover:text-invert-fg"
+    >
+      {label}
+    </button>
+  );
+}
+
+function Section({
+  group,
+  open,
+  onToggle,
+}: {
+  group: TunableGroup;
+  open: boolean;
+  onToggle: () => void;
+}) {
+  return (
+    <div className="border-b border-line last:border-b-0">
+      <button
+        type="button"
+        onClick={onToggle}
+        className="hud-label flex w-full items-center justify-between px-3 py-2 text-muted hover:text-ink"
+        aria-expanded={open}
+      >
+        {group.title}
+        <span aria-hidden className="text-faint">
+          {open ? "–" : "+"}
+        </span>
+      </button>
+      {open && (
+        <div className="flex flex-col gap-2 px-3 pb-3">
+          {Object.entries(group.defs).map(([key, def]) => (
+            <Row key={key} groupId={group.id} tunableKey={key} def={def} />
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
+
+function Row({
+  groupId,
+  tunableKey,
+  def,
+}: {
+  groupId: string;
+  tunableKey: string;
+  def: TunableGroup["defs"][string];
+}) {
+  const storeKey = `${groupId}.${tunableKey}`;
+  const value = useTunerStore((s) => s.values[storeKey] ?? def.default);
+  const setValue = useTunerStore((s) => s.setValue);
+  const modified = value !== def.default;
+
+  return (
+    <label className="flex flex-col gap-1">
+      <span className="flex items-center justify-between">
+        <span
+          className={`font-mono text-[10px] tracking-[0.08em] uppercase ${
+            modified ? "text-accent-ink" : "text-muted"
+          }`}
+        >
+          {def.label}
+        </span>
+        <input
+          type="number"
+          value={round(value)}
+          min={def.min}
+          max={def.max}
+          step={def.step}
+          onChange={(e) => {
+            const v = Number(e.target.value);
+            if (!Number.isNaN(v)) setValue(groupId, tunableKey, v);
+          }}
+          className="w-[72px] border border-line bg-bg px-1 py-0.5 text-right font-mono text-[11px] text-ink focus:outline-none focus:border-line-strong"
+        />
+      </span>
+      <input
+        type="range"
+        value={value}
+        min={def.min}
+        max={def.max}
+        step={def.step}
+        onChange={(e) => setValue(groupId, tunableKey, Number(e.target.value))}
+        className="h-1 w-full cursor-ew-resize accent-[var(--accent)]"
+      />
+    </label>
+  );
+}
+
+function round(v: number): number {
+  return Math.round(v * 10000) / 10000;
+}
diff --git a/frontend/apps/artcraft-website-next/src/components/landing/hero-tunables.ts b/frontend/apps/artcraft-website-next/src/components/landing/hero-tunables.ts
new file mode 100644
index 0000000000..9967904b3d
--- /dev/null
+++ b/frontend/apps/artcraft-website-next/src/components/landing/hero-tunables.ts
@@ -0,0 +1,62 @@
+// Every tweakable constant of the hero wordmark, registered with the dev
+// tuner (see TUNER.md). Defaults here ARE the shipped values — tune live,
+// copy the JSON from the panel, then update the defaults.
+
+import { defineTunables } from "@/lib/tuner";
+
+export const formationTuner = defineTunables("formation", "Formation", {
+  ballScale: { label: "Ball scale", min: 0.5, max: 2.5, step: 0.05, default: 1 },
+  sizeMin: { label: "Size min ×", min: 0.05, max: 0.6, step: 0.01, default: 0.18 },
+  sizeMax: { label: "Size max ×", min: 0.2, max: 1.4, step: 0.01, default: 0.66 },
+  sizeNoiseScale: { label: "Size noise px", min: 30, max: 400, step: 5, default: 130 },
+  sizeRoughen: { label: "Size roughen", min: 0, max: 1, step: 0.02, default: 0.4 },
+  gap: { label: "Gap px", min: 0, max: 6, step: 0.1, default: 0.6 },
+  depth: { label: "Depth ×", min: 0.2, max: 5, step: 0.1, default: 1.9 },
+  density: { label: "Fill density", min: 0.2, max: 3, step: 0.05, default: 1 },
+  edgeMargin: { label: "Edge margin", min: 0, max: 1, step: 0.05, default: 0.55 },
+  seed: { label: "Seed", min: 1, max: 9999, step: 1, default: 1013 },
+});
+
+export const physicsTuner = defineTunables("physics", "Physics", {
+  spring: { label: "Spring", min: 5, max: 140, step: 1, default: 46 },
+  damping: { label: "Damping", min: 1, max: 14, step: 0.1, default: 5.2 },
+  pushRadius: { label: "Push radius", min: 40, max: 450, step: 5, default: 180 },
+  pushStrength: { label: "Push strength", min: 1000, max: 80000, step: 500, default: 23000 },
+  swirl: { label: "Swirl", min: 0, max: 1.5, step: 0.05, default: 0.55 },
+  popZ: { label: "Pop toward viewer", min: 0, max: 2, step: 0.05, default: 0.6 },
+  bobAmp: { label: "Idle bob px", min: 0, max: 8, step: 0.1, default: 1.4 },
+  scatter: { label: "Intro scatter px", min: 0, max: 1400, step: 20, default: 480 },
+});
+
+export const lightTuner = defineTunables("light", "Cursor & Light", {
+  intensityDark: { label: "Cursor int (dark)", min: 0, max: 220000, step: 1000, default: 58000 },
+  intensityLight: { label: "Cursor int (light)", min: 0, max: 220000, step: 1000, default: 30000 },
+  idleDim: { label: "Idle dim", min: 0, max: 1, step: 0.05, default: 0.3 },
+  lightZ: { label: "Light z", min: 30, max: 500, step: 5, default: 130 },
+  lightRange: { label: "Light range", min: 100, max: 3000, step: 50, default: 900 },
+  keyIntensity: { label: "Back key (dark)", min: 0, max: 8, step: 0.1, default: 2.2 },
+  counterIntensity: { label: "Counter rim (dark)", min: 0, max: 4, step: 0.05, default: 0.7 },
+  frontFill: { label: "Front fill (dark)", min: 0, max: 1, step: 0.01, default: 0.06 },
+  ambientDark: { label: "Ambient (dark)", min: 0, max: 1, step: 0.01, default: 0.05 },
+  ambientLight: { label: "Ambient (light)", min: 0, max: 2, step: 0.05, default: 0.55 },
+  dirLight: { label: "Key (light)", min: 0, max: 3, step: 0.05, default: 0.75 },
+});
+
+export const materialTuner = defineTunables("material", "Material", {
+  roughnessDark: { label: "Roughness (dark)", min: 0, max: 1, step: 0.02, default: 0.42 },
+  metalnessDark: { label: "Metalness (dark)", min: 0, max: 1, step: 0.02, default: 0.5 },
+  clearcoat: { label: "Clearcoat (dark)", min: 0, max: 1, step: 0.02, default: 0.9 },
+  clearcoatRoughness: { label: "Coat rough (dark)", min: 0, max: 1, step: 0.02, default: 0.22 },
+  roughnessLight: { label: "Roughness (light)", min: 0, max: 1, step: 0.02, default: 0.3 },
+  metalnessLight: { label: "Metalness (light)", min: 0, max: 1, step: 0.02, default: 0.15 },
+  envLight: { label: "Env int (light)", min: 0, max: 2, step: 0.05, default: 0.55 },
+  accentShare: { label: "Accent share", min: 0, max: 0.3, step: 0.005, default: 0.05 },
+});
+
+export const haloTuner = defineTunables("halo", "Halo", {
+  size: { label: "Size px", min: 200, max: 1800, step: 20, default: 720 },
+  alphaDark: { label: "Alpha (dark)", min: 0, max: 1, step: 0.02, default: 0.5 },
+  alphaLight: { label: "Alpha (light)", min: 0, max: 0.6, step: 0.01, default: 0.14 },
+  z: { label: "Z offset", min: -400, max: 0, step: 5, default: -90 },
+  falloff: { label: "Falloff", min: 0.5, max: 6, step: 0.1, default: 2.6 },
+});
diff --git a/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx b/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx
index 875b2586a1..d40bb6ef9b 100644
--- a/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx
+++ b/frontend/apps/artcraft-website-next/src/components/landing/hero-wordmark.tsx
@@ -12,12 +12,19 @@ import { Canvas, useFrame, useThree } from "@react-three/fiber";
 import * as THREE from "three";
 import { RoomEnvironment } from "three/examples/jsm/environments/RoomEnvironment.js";
 import { watchThemeColors, type ThemeColors } from "@/lib/theme-colors";
+import { useTunerStore } from "@/lib/tuner";
 import {
   sampleWordmark,
   WordmarkSim,
-  DEFAULT_PARAMS,
   type SampledWordmark,
 } from "./wordmark-sim";
+import {
+  formationTuner,
+  physicsTuner,
+  lightTuner,
+  materialTuner,
+  haloTuner,
+} from "./hero-tunables";
 
 const WORDMARK = "artcraft";
 const FONT_WEIGHT = 700;
@@ -62,7 +69,8 @@ export default function HeroWordmark() {
   }, [ready]);
 
   // Rasterize + sample once the display font is really loaded; re-sample when
-  // the container width changes meaningfully (not on mobile URL-bar jitter).
+  // the container width changes meaningfully (not on mobile URL-bar jitter)
+  // or when a Formation tunable moves in the dev tuner.
   useEffect(() => {
     if (!ready) return;
     const container = containerRef.current;
@@ -72,9 +80,9 @@ export default function HeroWordmark() {
     let lastWidth = 0;
     let timer: ReturnType<typeof setTimeout> | undefined;
 
-    const build = async () => {
+    const build = async (force = false) => {
       const width = container.clientWidth;
-      if (!width || width === lastWidth) return;
+      if (!width || (!force && width === lastWidth)) return;
       lastWidth = width;
 
       const family = getComputedStyle(container).fontFamily;
@@ -85,7 +93,8 @@ export default function HeroWordmark() {
       }
       if (cancelled) return;
 
-      const spacing = Math.min(18, Math.max(11, width / 62));
+      const { ballScale, ...formation } = formationTuner.read();
+      const spacing = Math.min(18, Math.max(11, width / 62)) * ballScale;
       setSample(
         sampleWordmark({
           text: WORDMARK,
@@ -93,7 +102,7 @@ export default function HeroWordmark() {
           fontWeight: FONT_WEIGHT,
           targetWidth: Math.min(width * 0.88, 1280),
           spacing,
-          layers: width < 720 ? 2 : 3,
+          formation,
         }),
       );
     };
@@ -104,10 +113,22 @@ export default function HeroWordmark() {
       timer = setTimeout(build, 350);
     });
     ro.observe(container);
+
+    // Formation tunables change the arrangement itself — debounce a rebuild.
+    let lastFormation = JSON.stringify(formationTuner.read());
+    const unsubscribe = useTunerStore.subscribe(() => {
+      const now = JSON.stringify(formationTuner.read());
+      if (now === lastFormation) return;
+      lastFormation = now;
+      clearTimeout(timer);
+      timer = setTimeout(() => build(true), 250);
+    });
+
     return () => {
       cancelled = true;
       clearTimeout(timer);
       ro.disconnect();
+      unsubscribe();
     };
   }, [ready]);
 
@@ -221,9 +242,10 @@ const HALO_FRAGMENT = /* glsl */ `
   varying vec2 vUv;
   uniform vec3 uColor;
   uniform float uAlpha;
+  uniform float uFalloff;
   void main() {
     float d = distance(vUv, vec2(0.5)) * 2.0;
-    float a = pow(clamp(1.0 - d, 0.0, 1.0), 2.6);
+    float a = pow(clamp(1.0 - d, 0.0, 1.0), uFalloff);
     gl_FragColor = vec4(uColor, a * uAlpha);
   }
 `;
@@ -240,9 +262,20 @@ function BallField({
   const meshRef = useRef<THREE.InstancedMesh>(null);
   const lightRef = useRef<THREE.PointLight>(null);
   const haloRef = useRef<THREE.Mesh>(null);
+  const ambientRef = useRef<THREE.AmbientLight>(null);
+  const keyRef = useRef<THREE.DirectionalLight>(null);
+  const counterRef = useRef<THREE.DirectionalLight>(null);
+  const fillRef = useRef<THREE.DirectionalLight>(null);
   const lightPos = useRef(new THREE.Vector3(0, 120, 0));
-  const sim = useMemo(() => new WordmarkSim(sample), [sample]);
+  const sim = useMemo(
+    () => new WordmarkSim(sample, physicsTuner.read().scatter),
+    [sample],
+  );
   const dummy = useMemo(() => new THREE.Object3D(), []);
+  // Reactive so recoloring reruns when the accent share slider moves.
+  const accentShare = useTunerStore(
+    (s) => s.values["material.accentShare"] ?? 0.05,
+  );
 
   const dark = useMemo(() => {
     const c = new THREE.Color(colors.bg);
@@ -261,6 +294,7 @@ function BallField({
             value: new THREE.Color(dark ? "#a8c4ff" : colors.accent),
           },
           uAlpha: { value: dark ? 0.5 : 0.14 },
+          uFalloff: { value: 2.6 },
         },
         transparent: true,
         depthWrite: false,
@@ -285,7 +319,7 @@ function BallField({
     const c = new THREE.Color();
     const rand = seeded(4242);
     for (let i = 0; i < sim.n; i++) {
-      if (rand() < 0.05) {
+      if (rand() < accentShare) {
         c.copy(accent);
         if (dark) c.multiplyScalar(0.8);
       } else {
@@ -294,14 +328,20 @@ function BallField({
       mesh.setColorAt(i, c);
     }
     if (mesh.instanceColor) mesh.instanceColor.needsUpdate = true;
-  }, [colors, sim, dark]);
+  }, [colors, sim, dark, accentShare]);
 
   useFrame((state, delta) => {
     const mesh = meshRef.current;
     if (!mesh) return;
     const p = pointer.current;
 
-    sim.step(delta, p.x, p.y, p.active, DEFAULT_PARAMS);
+    // Live tuner values — read every frame so slider changes apply instantly.
+    const phys = physicsTuner.read();
+    const lt = lightTuner.read();
+    const mt = materialTuner.read();
+    const ht = haloTuner.read();
+
+    sim.step(delta, p.x, p.y, p.active, phys);
 
     for (let i = 0; i < sim.n; i++) {
       dummy.position.set(sim.x[i], sim.y[i], sim.z[i]);
@@ -322,22 +362,50 @@ function BallField({
     lightRef.current?.position.set(
       lightPos.current.x,
       lightPos.current.y,
-      130,
+      lt.lightZ,
     );
     haloRef.current?.position.set(
       lightPos.current.x,
       lightPos.current.y,
-      -90,
+      ht.z,
     );
 
     // At rest the word sits in near-eclipse; approaching with the cursor
     // brings the light up to full.
     const light = lightRef.current;
     if (light) {
-      const full = dark ? 58000 : 30000;
-      const target = p.active ? full : full * 0.3;
+      light.distance = lt.lightRange;
+      const full = dark ? lt.intensityDark : lt.intensityLight;
+      const target = p.active ? full : full * lt.idleDim;
       light.intensity += (target - light.intensity) * k;
     }
+
+    // Rig + material + halo bindings.
+    if (ambientRef.current) {
+      ambientRef.current.intensity = dark ? lt.ambientDark : lt.ambientLight;
+    }
+    if (keyRef.current) {
+      keyRef.current.intensity = dark ? lt.keyIntensity : lt.dirLight;
+    }
+    if (counterRef.current) counterRef.current.intensity = lt.counterIntensity;
+    if (fillRef.current) fillRef.current.intensity = lt.frontFill;
+
+    const mat = mesh.material as THREE.MeshPhysicalMaterial &
+      THREE.MeshStandardMaterial;
+    if (dark) {
+      mat.roughness = mt.roughnessDark;
+      mat.metalness = mt.metalnessDark;
+      mat.clearcoat = mt.clearcoat;
+      mat.clearcoatRoughness = mt.clearcoatRoughness;
+    } else {
+      mat.roughness = mt.roughnessLight;
+      mat.metalness = mt.metalnessLight;
+      mat.envMapIntensity = mt.envLight;
+    }
+
+    haloMaterial.uniforms.uAlpha.value = dark ? ht.alphaDark : ht.alphaLight;
+    haloMaterial.uniforms.uFalloff.value = ht.falloff;
+    haloRef.current?.scale.setScalar(ht.size / 720);
   });
 
   return (
@@ -353,15 +421,15 @@ function BallField({
         // rims the top edges, a faint counter-rim catches the lower-right,
         // and the cursor light does the actual revealing.
         <>
-          <ambientLight intensity={0.05} />
-          <directionalLight position={[-160, 340, -460]} intensity={2.2} color="#e9f1ff" />
-          <directionalLight position={[430, -180, -380]} intensity={0.7} color="#7fa8e8" />
-          <directionalLight position={[0, -60, 520]} intensity={0.06} />
+          <ambientLight ref={ambientRef} intensity={0.05} />
+          <directionalLight ref={keyRef} position={[-160, 340, -460]} intensity={2.2} color="#e9f1ff" />
+          <directionalLight ref={counterRef} position={[430, -180, -380]} intensity={0.7} color="#7fa8e8" />
+          <directionalLight ref={fillRef} position={[0, -60, 520]} intensity={0.06} />
         </>
       ) : (
         <>
-          <ambientLight intensity={0.55} />
-          <directionalLight position={[-260, 340, 420]} intensity={0.75} />
+          <ambientLight ref={ambientRef} intensity={0.55} />
+          <directionalLight ref={keyRef} position={[-260, 340, 420]} intensity={0.75} />
           <directionalLight position={[180, 260, -420]} intensity={0.5} color="#eef3ff" />
         </>
       )}
diff --git a/frontend/apps/artcraft-website-next/src/components/landing/wordmark-sim.ts b/frontend/apps/artcraft-website-next/src/components/landing/wordmark-sim.ts
index 26b01dfbd4..a22cb4051e 100644
--- a/frontend/apps/artcraft-website-next/src/components/landing/wordmark-sim.ts
+++ b/frontend/apps/artcraft-website-next/src/components/landing/wordmark-sim.ts
@@ -1,8 +1,9 @@
 // Wordmark ball field: the brand name rasterized to a mask, then filled with
-// small 3D balls on a jittered close-packed lattice a few layers deep. The
-// balls separate under the cursor's push and rejoin on their home springs; a
-// 3D collision pass keeps them from intersecting, so the text reads as a
-// solid object built from spheres rather than a flat particle billboard.
+// small 3D balls by multi-pass dart throwing — big balls land first, smaller
+// ones settle into the gaps, like a pile that collided into the letter shape
+// (a faked impression, not a physics solve; it must run on laptops/phones).
+// The balls separate under the cursor's push and rejoin on their home
+// springs; a 3D collision pass keeps them from intersecting.
 //
 // Units are CSS pixels at the text's z=0 plane — the camera is fitted so one
 // world unit projects to one pixel there, which keeps pointer math trivial.
@@ -20,6 +21,20 @@ export type SampledWordmark = {
   height: number;
 };
 
+// All knobs of the arrangement — registered with the dev tuner in
+// hero-tunables.ts. Size factors are multiples of `spacing`.
+export type FormationParams = {
+  sizeMin: number;
+  sizeMax: number;
+  sizeNoiseScale: number; // px wavelength of the size clusters
+  sizeRoughen: number;    // 0..1 per-ball white-noise contribution
+  gap: number;            // px clearance between resting balls
+  depth: number;          // slab thickness, × spacing
+  density: number;        // dart-attempt multiplier
+  edgeMargin: number;     // 0..1 — how far inside the stroke big balls stay
+  seed: number;
+};
+
 // ————————————————————————————— sampling —————————————————————————————
 
 export function sampleWordmark(opts: {
@@ -27,12 +42,12 @@ export function sampleWordmark(opts: {
   fontFamily: string;
   fontWeight: number;
   targetWidth: number;
-  /** Lattice spacing in px — sets ball size (~spacing/2) and count. */
+  /** Base unit in px — ball sizes and slab depth scale from this. */
   spacing: number;
-  /** Depth layers (2–3 keeps it chunky without mush). */
-  layers: number;
+  formation: FormationParams;
 }): SampledWordmark {
-  const { text, fontFamily, fontWeight, targetWidth, spacing, layers } = opts;
+  const { text, fontFamily, fontWeight, targetWidth, spacing, formation } =
+    opts;
 
   // Each glyph is measured and drawn individually with a small manual gap:
   // no shaping ever runs across letters, so the font can't fuse tight pairs
@@ -75,90 +90,106 @@ export function sampleWordmark(opts: {
     return alpha[(y * width + x) * 4 + 3] > 127;
   };
 
-  const rand = mulberry32(1013);
-  const jitter = spacing * 0.13;
-  const rowH = spacing * (Math.SQRT2 / 2) * 1.22; // hex-ish row pitch
-  const balls: Ball[] = [];
-
-  // Organic sizing: a smooth spatial noise drifts the ball size across the
-  // word (clusters of big and small), white noise roughens it per ball. The
-  // neighbor cap below keeps every draw collision-safe, so variance only
-  // ever shrinks balls — which is exactly what reads as hand-made.
-  const sizeNoise = makeValueNoise(41);
-  const desiredRadius = (x: number, y: number) =>
-    spacing *
-    (0.24 +
-      0.36 * Math.pow(sizeNoise(x / 130, y / 130), 1.15) +
-      rand() * 0.16);
-
-  for (let layer = 0; layer < layers; layer++) {
-    const z = (layer - (layers - 1) / 2) * spacing * 0.92;
-    // Alternate layers shift half a cell both ways so depth neighbors nest
-    // into the gaps instead of stacking into columns.
-    const layerOff = layer % 2 === 0 ? 0 : spacing * 0.5;
-    let row = 0;
-    for (let y = pad * 0.5; y < height - pad * 0.5; y += rowH, row++) {
-      const rowOff = (row % 2 === 0 ? 0 : spacing * 0.5) + layerOff;
-      for (let x = pad * 0.5 + rowOff; x < width - pad * 0.5; x += spacing) {
-        const jx = x + (rand() - 0.5) * jitter * 2;
-        const jy = y + (rand() - 0.5) * jitter * 2;
-        if (!covered(Math.round(jx), Math.round(jy))) continue;
-        balls.push({
-          x: jx,
-          y: jy,
-          z: z + (rand() - 0.5) * jitter * 2,
-          r: desiredRadius(jx, jy), // desired; capped below
-        });
-      }
+  // Fast "random point inside the ink" sampling: collect covered pixels on a
+  // coarse stride once, then darts pick from that list with subpixel jitter.
+  const inkCells: number[] = [];
+  for (let y = 0; y < height; y += 2) {
+    for (let x = 0; x < width; x += 2) {
+      if (covered(x, y)) inkCells.push(y * width + x);
     }
   }
+  if (!inkCells.length) return { balls: [], width, height };
 
-  // Cap every radius at half its nearest-home-neighbor distance so the rest
-  // pose is non-overlapping regardless of jitter — collisions then only ever
-  // matter mid-shove, never in the settled wordmark.
-  capRadiiToNeighbors(balls, spacing);
+  const rand = mulberry32(formation.seed);
+  const sizeNoise = makeValueNoise(formation.seed + 41);
+  const rMin = spacing * formation.sizeMin;
+  const rMax = spacing * formation.sizeMax;
+  const halfDepth = (spacing * formation.depth) / 2;
 
-  return { balls, width, height };
-}
+  // Organic sizing: smooth spatial noise drifts the size in clusters across
+  // the word; white noise roughens it per ball.
+  const desiredRadius = (x: number, y: number) => {
+    const n = Math.pow(
+      sizeNoise(x / formation.sizeNoiseScale, y / formation.sizeNoiseScale),
+      1.15,
+    );
+    const roughened =
+      n * (1 - formation.sizeRoughen) + rand() * formation.sizeRoughen;
+    return rMin + (rMax - rMin) * roughened;
+  };
 
-function capRadiiToNeighbors(balls: Ball[], spacing: number) {
-  const cell = spacing * 2;
+  // A ball only counts as "inside the letter" if its center plus four cross
+  // points at ~edgeMargin·r are on ink — big balls stay inside the strokes,
+  // small ones may nestle right up to the edge, keeping letterforms crisp.
+  const insideStroke = (x: number, y: number, r: number) => {
+    const m = r * formation.edgeMargin;
+    return (
+      covered(Math.round(x), Math.round(y)) &&
+      covered(Math.round(x + m), Math.round(y)) &&
+      covered(Math.round(x - m), Math.round(y)) &&
+      covered(Math.round(x), Math.round(y + m)) &&
+      covered(Math.round(x), Math.round(y - m))
+    );
+  };
+
+  // Dart throwing with a 3D hash for overlap rejection. Three passes with a
+  // descending size floor: the big balls claim their spots first and the
+  // smaller ones settle into the leftover gaps — the arrangement reads like
+  // a settled pile instead of a grid.
+  const balls: Ball[] = [];
+  const cell = rMax * 2 + formation.gap;
   const grid = new Map<number, number[]>();
   const key = (x: number, y: number, z: number) =>
     (Math.floor(x / cell) * 73856093) ^
     (Math.floor(y / cell) * 19349663) ^
     (Math.floor(z / cell) * 83492791);
-  balls.forEach((b, i) => {
-    const k = key(b.x, b.y, b.z);
-    const bucket = grid.get(k);
-    if (bucket) bucket.push(i);
-    else grid.set(k, [i]);
-  });
 
-  const nearest = new Float32Array(balls.length).fill(Infinity);
-  for (let i = 0; i < balls.length; i++) {
-    const b = balls[i];
+  const fits = (x: number, y: number, z: number, r: number) => {
     for (let gz = -1; gz <= 1; gz++) {
       for (let gy = -1; gy <= 1; gy++) {
         for (let gx = -1; gx <= 1; gx++) {
           const bucket = grid.get(
-            key(b.x + gx * cell, b.y + gy * cell, b.z + gz * cell),
+            key(x + gx * cell, y + gy * cell, z + gz * cell),
           );
           if (!bucket) continue;
           for (const j of bucket) {
-            if (j === i) continue;
             const o = balls[j];
-            const d = Math.hypot(b.x - o.x, b.y - o.y, b.z - o.z);
-            if (d < nearest[i]) nearest[i] = d;
+            const dx = o.x - x;
+            const dy = o.y - y;
+            const dz = o.z - z;
+            const min = o.r + r + formation.gap;
+            if (dx * dx + dy * dy + dz * dz < min * min) return false;
           }
         }
       }
     }
+    return true;
+  };
+
+  const passes = [0.7, 0.35, 0]; // descending floor on the size range
+  const attemptsPerPass = Math.floor(
+    inkCells.length * 0.9 * formation.density,
+  );
+  for (const floor of passes) {
+    for (let a = 0; a < attemptsPerPass; a++) {
+      const c = inkCells[(rand() * inkCells.length) | 0];
+      const x = (c % width) + rand() * 2 - 1;
+      const y = Math.floor(c / width) + rand() * 2 - 1;
+      const z = (rand() * 2 - 1) * halfDepth;
+      let r = desiredRadius(x, y);
+      const passMin = rMin + (rMax - rMin) * floor;
+      if (r < passMin) r = passMin + (r - rMin) * 0.2;
+      if (!insideStroke(x, y, r)) continue;
+      if (!fits(x, y, z, r)) continue;
+      balls.push({ x, y, z, r });
+      const k = key(x, y, z);
+      const bucket = grid.get(k);
+      if (bucket) bucket.push(balls.length - 1);
+      else grid.set(k, [balls.length - 1]);
+    }
   }
-  for (let i = 0; i < balls.length; i++) {
-    const fit = nearest[i] * 0.5 - 0.4;
-    balls[i].r = Math.max(spacing * 0.15, Math.min(balls[i].r, fit));
-  }
+
+  return { balls, width, height };
 }
 
 // Deterministic bilinear value noise, 0..1 — smooth variation across space.
diff --git a/frontend/apps/artcraft-website-next/src/lib/tuner.ts b/frontend/apps/artcraft-website-next/src/lib/tuner.ts
new file mode 100644
index 0000000000..18b3522e90
--- /dev/null
+++ b/frontend/apps/artcraft-website-next/src/lib/tuner.ts
@@ -0,0 +1,133 @@
+// Live dev tuner (see TUNER.md).
+//
+// Any module can register a group of numeric tunables with `defineTunables`;
+// the TunerPanel renders every registered group with sliders + number inputs,
+// and consumers read live values per frame (or subscribe for rebuilds).
+// Values persist to localStorage so a refresh keeps the current tuning.
+//
+// POLICY: every new tweakable constant in this app gets registered here by
+// default — adding a slider is free, a missing one costs an iteration.
+
+import { create } from "zustand";
+
+export type TunableDef = {
+  label: string;
+  min: number;
+  max: number;
+  step: number;
+  default: number;
+};
+
+export type TunableGroup = {
+  id: string;
+  title: string;
+  order: number;
+  defs: Record<string, TunableDef>;
+};
+
+type TunerState = {
+  groups: Record<string, TunableGroup>;
+  /** Sparse overrides, keyed "group.key". Defaults live in the defs. */
+  values: Record<string, number>;
+  /** Bumped on every change — cheap signal for rebuild subscribers. */
+  version: number;
+  registerGroup: (
+    id: string,
+    title: string,
+    defs: Record<string, TunableDef>,
+  ) => void;
+  setValue: (groupId: string, key: string, value: number) => void;
+  resetAll: () => void;
+};
+
+const STORAGE_KEY = "artcraft-tuner";
+
+function loadStored(): Record<string, number> {
+  if (typeof window === "undefined") return {};
+  try {
+    const parsed = JSON.parse(localStorage.getItem(STORAGE_KEY) ?? "{}");
+    return typeof parsed === "object" && parsed !== null ? parsed : {};
+  } catch {
+    return {};
+  }
+}
+
+function save(values: Record<string, number>) {
+  try {
+    localStorage.setItem(STORAGE_KEY, JSON.stringify(values));
+  } catch {
+    // Storage may be unavailable (private mode); tuning just won't persist.
+  }
+}
+
+export const useTunerStore = create<TunerState>((set) => ({
+  groups: {},
+  values: loadStored(),
+  version: 0,
+  registerGroup: (id, title, defs) =>
+    set((s) =>
+      s.groups[id]
+        ? s
+        : {
+            groups: {
+              ...s.groups,
+              [id]: { id, title, order: Object.keys(s.groups).length, defs },
+            },
+          },
+    ),
+  setValue: (groupId, key, value) =>
+    set((s) => {
+      const values = { ...s.values, [`${groupId}.${key}`]: value };
+      save(values);
+      return { values, version: s.version + 1 };
+    }),
+  resetAll: () =>
+    set((s) => {
+      save({});
+      return { values: {}, version: s.version + 1 };
+    }),
+}));
+
+export type TunableReader<T extends Record<string, TunableDef>> = {
+  id: string;
+  defs: T;
+  /** Current values (defaults merged with overrides). Cheap; call per frame. */
+  read: () => { [K in keyof T]: number };
+};
+
+// Registers a tunable group (once) and returns a typed live reader.
+// Call at module scope in the file that owns the constants.
+export function defineTunables<T extends Record<string, TunableDef>>(
+  id: string,
+  title: string,
+  defs: T,
+): TunableReader<T> {
+  useTunerStore.getState().registerGroup(id, title, defs);
+  return {
+    id,
+    defs,
+    read: () => {
+      const { values } = useTunerStore.getState();
+      const out = {} as { [K in keyof T]: number };
+      for (const key in defs) {
+        const override = values[`${id}.${String(key)}`];
+        out[key] = override ?? defs[key].default;
+      }
+      return out;
+    },
+  };
+}
+
+// Merged snapshot of every registered group — used by the panel's copy
+// button so tuned values can be pasted back into code as new defaults.
+export function tunerSnapshot(): Record<string, Record<string, number>> {
+  const { groups, values } = useTunerStore.getState();
+  const out: Record<string, Record<string, number>> = {};
+  for (const g of Object.values(groups)) {
+    out[g.id] = {};
+    for (const key in g.defs) {
+      out[g.id][key] = values[`${g.id}.${key}`] ?? g.defs[key].default;
+    }
+  }
+  return out;
+}