feat: model colour selector

Floating swatch palette (bottom-left) + native custom picker. Colour is a
viewer preference persisted in localStorage; threads App → Viewer → Model
material. Defaults to brand red.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/client/App.tsx

@@ -2,6 +2,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 import { Viewer } from "./components/Viewer";
 import { StageOverlay } from "./components/StageOverlay";
 import { DesignsDrawer } from "./components/DesignsDrawer";
+import { ColorPicker } from "./components/ColorPicker";
 import { runJscad, parseParams, type Param } from "./engine";
 
 interface Msg {
@@ -45,6 +46,13 @@ export default function App() {
   const [designs, setDesigns] = useState<DesignSummary[]>([]);
   const [drawerOpen, setDrawerOpen] = useState(false);
   const [steppy, setSteppy] = useState(false); // STEP export in flight
+  const [color, setColor] = useState<string>(() => {
+    try {
+      return localStorage.getItem("chisel_color") || "#FF2D55";
+    } catch {
+      return "#FF2D55";
+    }
+  });
 
   const scrollRef = useRef<HTMLDivElement>(null);
   const captureRef = useRef<(() => string | null) | null>(null);
@@ -294,6 +302,15 @@ export default function App() {
     }
   }, [steppy, messages, title]);
 
+  const setModelColor = useCallback((c: string) => {
+    setColor(c);
+    try {
+      localStorage.setItem("chisel_color", c);
+    } catch {
+      /* ignore */
+    }
+  }, []);
+
   const fitKey = String(designVersion);
 
   return (
@@ -393,9 +410,10 @@ export default function App() {
       </aside>
 
       <main className="stage">
-        <Viewer stl={stl} fitKey={fitKey} captureRef={captureRef} />
+        <Viewer stl={stl} fitKey={fitKey} color={color} captureRef={captureRef} />
         <StageOverlay stage={stage} label={STAGE_LABEL[stage]} />
         {title && <div className="title-chip">{title}</div>}
+        {stl && !stage && <ColorPicker color={color} onChange={setModelColor} />}
         {stl && !stage && (
           <div className="toolbar">
             <button onClick={() => setDesignVersion((v) => v + 1)} className="ghost" title="Fit to view">

src/client/components/ColorPicker.tsx

@@ -0,0 +1,34 @@
+// Model colour selector: a row of preset swatches + a native custom picker.
+// Colour is a viewer preference (persisted in localStorage by App), not part of
+// the geometry — it only sets the preview material.
+const PRESETS = [
+  "#FF2D55", // radical red
+  "#FF7A00", // orange
+  "#FFD400", // yellow
+  "#3ddc84", // green
+  "#4a9eff", // blue
+  "#B47CFF", // purple
+  "#C8CCD4", // steel
+  "#F2F2F0", // white
+  "#1A1A1A", // graphite
+];
+
+export function ColorPicker({ color, onChange }: { color: string; onChange: (c: string) => void }) {
+  return (
+    <div className="colorpicker">
+      {PRESETS.map((c) => (
+        <button
+          key={c}
+          className={`swatch ${c.toLowerCase() === color.toLowerCase() ? "active" : ""}`}
+          style={{ background: c }}
+          title={c}
+          onClick={() => onChange(c)}
+        />
+      ))}
+      <label className="swatch custom" title="Custom colour">
+        <input type="color" value={color} onChange={(e) => onChange(e.target.value)} />
+        <span>+</span>
+      </label>
+    </div>
+  );
+}

src/client/components/Viewer.tsx

@@ -4,7 +4,7 @@ import { OrbitControls, GizmoHelper, GizmoViewport, Grid, Center, Bounds } from
 import { STLLoader } from "three/examples/jsm/loaders/STLLoader.js";
 import type { BufferGeometry } from "three";
 
-function Model({ stl }: { stl: ArrayBuffer }) {
+function Model({ stl, color }: { stl: ArrayBuffer; color: string }) {
   const geometry = useMemo<BufferGeometry>(() => {
     const g = new STLLoader().parse(stl.slice(0));
     g.computeVertexNormals();
@@ -16,7 +16,7 @@ function Model({ stl }: { stl: ArrayBuffer }) {
   return (
     <Center>
       <mesh geometry={geometry} castShadow receiveShadow>
-        <meshStandardMaterial color="#FF2D55" metalness={0.15} roughness={0.55} />
+        <meshStandardMaterial color={color} metalness={0.15} roughness={0.55} />
       </mesh>
     </Center>
   );
@@ -52,10 +52,11 @@ interface ViewerProps {
   // Changes ONLY when a new design loads (or the user hits Fit). Param tweaks keep
   // the same fitKey so the camera holds still and size changes stay visible.
   fitKey: string;
+  color: string;
   captureRef: MutableRefObject<(() => string | null) | null>;
 }
 
-export function Viewer({ stl, fitKey, captureRef }: ViewerProps) {
+export function Viewer({ stl, fitKey, color, captureRef }: ViewerProps) {
   const controls = useRef(null);
   return (
     <Canvas
@@ -79,7 +80,7 @@ export function Viewer({ stl, fitKey, captureRef }: ViewerProps) {
       {/* key={fitKey} → Bounds refits exactly once per new design, not per param. */}
       {stl && (
         <Bounds key={fitKey} fit clip margin={1.35}>
-          <Model stl={stl} />
+          <Model stl={stl} color={color} />
         </Bounds>
       )}
       <OrbitControls ref={controls} makeDefault enableDamping />

src/client/styles.css

@@ -82,6 +82,15 @@ body { background: var(--bg); color: var(--text); font-family: var(--mono); }
 
 .title-chip { position: absolute; top: 18px; left: 18px; font-family: var(--display); font-weight: 600; font-size: 14px; color: var(--text); background: rgba(11,11,9,.7); border: 1px solid var(--line); border-radius: 20px; padding: 6px 14px; backdrop-filter: blur(6px); max-width: 40%; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
 
+/* --- Colour selector --- */
+.colorpicker { position: absolute; bottom: 18px; left: 18px; display: flex; gap: 6px; align-items: center; background: rgba(11,11,9,.7); border: 1px solid var(--line); border-radius: 24px; padding: 7px 10px; backdrop-filter: blur(8px); }
+.swatch { width: 20px; height: 20px; border-radius: 50%; border: 2px solid transparent; cursor: pointer; padding: 0; box-shadow: inset 0 0 0 1px rgba(255,255,255,.12); transition: transform .1s; }
+.swatch:hover { transform: scale(1.15); }
+.swatch.active { border-color: #fff; }
+.swatch.custom { position: relative; display: inline-flex; align-items: center; justify-content: center; background: conic-gradient(from 0deg, #ff2d55, #ffd400, #3ddc84, #4a9eff, #b47cff, #ff2d55); color: #fff; font-weight: 700; font-size: 13px; overflow: hidden; }
+.swatch.custom span { text-shadow: 0 0 3px rgba(0,0,0,.7); pointer-events: none; }
+.swatch.custom input { position: absolute; inset: 0; opacity: 0; cursor: pointer; }
+
 /* --- Progress overlay --- */
 .overlay { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; background: radial-gradient(circle at center, rgba(11,11,9,.55), rgba(11,11,9,.82)); backdrop-filter: blur(2px); z-index: 20; animation: fade .2s ease; }
 @keyframes fade { from { opacity: 0; } to { opacity: 1; } }