perf: use cached body dimensions in tick, remove redundant style sets

lib/gravity-engine.ts

@@ -192,36 +192,23 @@ export class GravityEngine {
 
     this.bodies.forEach((body) => {
       if (body.isDragging) {
-        // Only update visually while dragging, physics are paused
-        body.el.style.position = "fixed";
-        body.el.style.left = "0px";
-        body.el.style.top = "0px";
         body.el.style.transform = `translate(${body.x}px, ${body.y}px)`;
         return;
       }
 
-      // Apply Gravity
       body.vy += gravity;
       body.x += body.vx;
       body.y += body.vy;
 
-      // Apply Air Friction
       body.vx *= 0.99;
       body.vy *= 0.99;
 
-      const rect = body.el.getBoundingClientRect();
-
-      // Floor Collision
-      if (body.y + rect.height > floorY) {
-        body.y = floorY - rect.height;
+      if (body.y + body.height > floorY) {
+        body.y = floorY - body.height;
         body.vy *= bounce;
-        body.vx *= 0.9; // Ground friction
+        body.vx *= 0.9;
       }
 
-      // Render Step
-      body.el.style.position = "fixed";
-      body.el.style.left = "0px";
-      body.el.style.top = "0px";
       body.el.style.transform = `translate(${body.x}px, ${body.y}px)`;
     });