Fix GradientBlinds scroll drift on mobile

- Added isMobile detection (<= 768px) in GradientBlinds.tsx
- Updated onPointerMove to calculate container-relative coordinates immediately on mobile
- Updated animation loop to skip scroll-based target updates on mobile
- Prevents spotlight from drifting across the background during scroll inertia on mobile devices

Co-authored-by: ragusa-it <196988693+ragusa-it@users.noreply.github.com>

src/components/effects/GradientBlinds.tsx

@@ -66,6 +66,7 @@ const GradientBlinds: React.FC<GradientBlindsProps> = ({
   const mouseTargetRef = useRef<[number, number]>([0, 0]);
   // Optimization: store raw pointer position (viewport coords) to decouple event handling from calculation
   const pointerPosRef = useRef<{ x: number; y: number } | null>(null);
+  const isMobileRef = useRef<boolean>(false);
   const lastTimeRef = useRef<number>(0);
   const firstResizeRef = useRef<boolean>(true);
   const rectRef = useRef<DOMRect | null>(null);
@@ -283,6 +284,7 @@ void main() {
       const rect = container.getBoundingClientRect();
       rectRef.current = rect;
       if (typeof window !== 'undefined') {
+        isMobileRef.current = window.innerWidth <= 768;
         scrollPosRef.current = { x: window.scrollX, y: window.scrollY };
       }
       renderer.setSize(rect.width, rect.height);
@@ -311,7 +313,30 @@ void main() {
     ro.observe(container);
 
     const onPointerMove = (e: PointerEvent) => {
-      pointerPosRef.current = { x: e.clientX, y: e.clientY };
+      if (isMobileRef.current) {
+        // On mobile, calculate relative position immediately and store in target.
+        // This prevents the "ghost drift" effect when scrolling with inertia after lifting finger,
+        // because we won't be updating the target based on scroll position in the loop.
+        const scale = (renderer as unknown as { dpr?: number }).dpr || 1;
+        let x, y;
+
+        if (rectRef.current) {
+          const dx = window.scrollX - scrollPosRef.current.x;
+          const dy = window.scrollY - scrollPosRef.current.y;
+          const rectLeft = rectRef.current.left - dx;
+          const rectTop = rectRef.current.top - dy;
+          x = (e.clientX - rectLeft) * scale;
+          y = (rectRef.current.height - (e.clientY - rectTop)) * scale;
+        } else {
+          const rect = canvas.getBoundingClientRect();
+          x = (e.clientX - rect.left) * scale;
+          y = (rect.height - (e.clientY - rect.top)) * scale;
+        }
+        mouseTargetRef.current = [x, y];
+        pointerPosRef.current = null; // Ensure loop doesn't override
+      } else {
+        pointerPosRef.current = { x: e.clientX, y: e.clientY };
+      }
     };
 
     const loop = (t: number) => {