diff --git a/debug/tick.ts b/debug/tick.ts
index 6179731..d0ddd09 100644
--- a/debug/tick.ts
+++ b/debug/tick.ts
@@ -43,10 +43,18 @@ export function OrbitDemo() {
   cx.scale(1 / 2, 1 / 2);
   cx.translate(512, 512);
 
-  const masses: { x: number; y: number; r: number; m: number; c: string }[] = [
-    { x: 0, y: 0, r: 10, m: 10000, c: "yellow" },
-    { x: -200, y: 200, r: 4, m: 4, c: "red" },
-    { x: -450, y: 0, r: 5, m: 5, c: "blue" },
+  const masses: {
+    x: number;
+    y: number;
+    vx: number;
+    vy: number;
+    r: number;
+    m: number;
+    c: string;
+  }[] = [
+    { x: 0, y: 0, vx: 0, vy: 0, r: 10, m: 10000, c: "yellow" },
+    { x: -200, y: 200, vx: 100, vy: 100, r: 4, m: 4, c: "red" },
+    { x: -450, y: 0, vx: 0, vy: 100, r: 5, m: 5, c: "blue" },
   ];
 
   const tickSource = tick(16);
@@ -61,12 +69,13 @@ export function OrbitDemo() {
         case "physics":
           break;
         case "render":
+          const [, dt] = tick;
           cx.fillStyle = "black";
           cx.fillRect(-512, -512, 1024, 1024);
-          masses.forEach(({ x, y, r, c }) => {
+          masses.forEach(({ x, y, vx, vy, r, c }) => {
             cx.fillStyle = c;
             cx.beginPath();
-            cx.arc(x, y, r, 0, Math.PI * 2);
+            cx.arc(x + vx * dt, y + vy * dt, r, 0, Math.PI * 2);
             cx.fill();
           });
           break;