diff --git a/examples/main.ts b/examples/main.ts
index d0ce102e1..58c796062 100644
--- a/examples/main.ts
+++ b/examples/main.ts
@@ -48,12 +48,17 @@ export class Milestone {
   }
 }
 
+let circle = new nc.Circle(100, {
+  x: 200,
+  y: 200
+})
 export const defaultScene = new nc.Scene(
   new nc.Circle(100, {
     x: 200,
     y: 200
-  })
-  .animate(nc.focusOn().withAttr({ duration: 0.3 }))
+  }).animate(nc.useAnimate<nc.Circle, {}>(ctx => {
+    ctx.widget.pos.value = nc.pp(0.5, 0.5)
+  }).withAttr({ duration: 1 }))
 )
 
 const left = document.querySelector('.left') as HTMLDivElement
@@ -70,10 +75,10 @@ window.addEventListener('keydown', e => {
   switch (e.key) {
     case 'ArrowLeft':
       left.dispatchEvent(new Event('click'))
-      break;
+      break
     case 'ArrowRight':
       right.dispatchEvent(new Event('click'))
-      break;
+      break
   }
 })
 
diff --git a/packages/core/src/app.ts b/packages/core/src/app.ts
index eab959e0d..41c58e271 100644
--- a/packages/core/src/app.ts
+++ b/packages/core/src/app.ts
@@ -77,6 +77,7 @@ export class App {
         plugin.beforeCheckout(this, scene)
     }
     this.scene = scene
+    this.scene.root.canvasSize = [this.element.width, this.element.height]
     this.scene.startTime = performance.now()
     for (const plugin of this.plugins) {
       if (plugin.onCheckout)
@@ -111,11 +112,11 @@ export class App {
         plugin.onUpdate(app, app.scene.elapsed)
     }
 
+    app.scene.root.canvasSize = [app.element.width, app.element.height]
     app.scene.root.update(
       app.scene.elapsed,
       app.ck,
       canvas,
-      app,
     )
 
     if (app.config.unit === 'frame')
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index c5fd4969d..157939f7a 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -16,3 +16,4 @@ export * from './localApp'
 export * from './event'
 
 export * from './prop'
+export * from './physical'
diff --git a/packages/core/src/localApp.ts b/packages/core/src/localApp.ts
index c74ce227f..e4cef5e88 100644
--- a/packages/core/src/localApp.ts
+++ b/packages/core/src/localApp.ts
@@ -54,32 +54,24 @@ export class LocalApp {
   }
 
   static update(app: LocalApp): void {
-    for (const plugin of app.plugins)
-      plugin.beforeUpdate(app, app.scene.elapsed)
-
-    initial(app.scene.root, app.ck, app.canvas)
-    // Contrast the old widget and the new widget and update them.
-    for (const plugin of app.plugins)
-      plugin.beforePatch(app, app.scene.elapsed, app.last, app.scene.root)
+    if (!app.playing)
+      return
 
     for (const plugin of app.plugins) {
-      plugin.onPatch(app, app.scene.elapsed, app.last, app.scene.root)
+      if (plugin.beforeUpdate)
+        plugin.beforeUpdate(app, app.scene.elapsed)
+    }
+    for (const plugin of app.plugins) {
+      if (plugin.onUpdate)
+        plugin.onUpdate(app, app.scene.elapsed)
     }
-    (function draw(widget: Widget) {
-      widget.init(app.ck)
-      app.canvas.save()
-      // widget.update(app.canvas)
-      for (const child of widget.children) draw(child)
-
-      app.canvas.restore()
-    })(app.scene.root)
-
-    // Animating.
-    app.scene.root.runAnimation(app.scene.elapsed, app.ck)
-
-    for (const plugin of app.plugins) plugin.onUpdate(app, app.scene.elapsed)
 
-    app.scene.elapsed += 1
+    app.scene.root.canvasSize = [app.width, app.height]
+    app.scene.root.update(
+      app.scene.elapsed,
+      app.ck,
+      app.canvas,
+    )
   }
 
   /**
diff --git a/packages/core/src/physical.ts b/packages/core/src/physical.ts
index c8fbb32ec..678ad5575 100644
--- a/packages/core/src/physical.ts
+++ b/packages/core/src/physical.ts
@@ -15,31 +15,31 @@ export class Length {
   }
 }
 
-export function r(value: number) {
+export function rl(value: number) {
   return new Length('raw', value)
 }
 
-export function p(value: number) {
+export function pl(value: number) {
   return new Length('percent', value)
 }
 
 export class Position {
   constructor(public type: LengthUnitType, public x: number, public y: number) {}
 
-  resolve(originX: number, originY: number): [number, number] {
+  resolve(width: number, height: number): [number, number] {
     switch (this.type) {
       case 'raw':
         return [this.x, this.y]
       case 'percent':
-        return [this.x * originX, this.y * originY]
+        return [this.x * width, this.y * height]
     }
   }
 }
 
-export function rp(value: number) {
-  return new Length('raw', value)
+export function rp(x: number, y: number) {
+  return new Position('raw', x, y)
 }
 
-export function pp(value: number) {
-  return new Length('percent', value)
+export function pp(x: number, y: number) {
+  return new Position('percent', x, y)
 }
diff --git a/packages/core/src/scene.ts b/packages/core/src/scene.ts
index 807b84996..b681ce610 100644
--- a/packages/core/src/scene.ts
+++ b/packages/core/src/scene.ts
@@ -1,11 +1,21 @@
-import type { Widget } from './widget'
+import { Widget } from './widget'
+
+export class RootWidget extends Widget {
+  canvasSize: [number, number]
+
+  constructor() {
+    super()
+  }
+}
 
 export class Scene {
   elapsed = 0
   startTime: number
+  root: RootWidget = new RootWidget()
 
-  constructor(public root: Widget) {
+  constructor(root: Widget) {
     this.root.status = 'live'
+    this.root.add(root)
   }
 }
 
diff --git a/packages/core/src/widget.ts b/packages/core/src/widget.ts
index d24f88a48..c9adccd4a 100644
--- a/packages/core/src/widget.ts
+++ b/packages/core/src/widget.ts
@@ -5,9 +5,12 @@ import type { Event, EventInstance } from './event'
 import { defineEvent } from './event'
 import type { WidgetPlugin } from './plugin'
 import type { AnimateFunction } from './apiAnimate'
-import type { ConvertToProp, Ref } from './prop'
+import type { ConvertToProp, Reactive, Ref } from './prop'
 import type { App } from './app'
-import { ref } from './prop'
+import { changed, reactive, ref } from './prop'
+import type { Position } from './physical'
+import { rp } from './physical'
+import { RootWidget } from './scene'
 
 export type WidgetRange = [number, number, number, number]
 // export type WidgetInstance<T extends Widget> = T
@@ -19,6 +22,7 @@ export interface WidgetOptions {
   style?: WidgetStyle
   x?: number
   y?: number
+  pos?: Position | [number, number]
   centerX?: number // The rotation center x of the widget.
   centerY?: number // The rotation center y of the widget.
   progress?: number
@@ -38,6 +42,7 @@ export interface WidgetStyle {
 
 export class Widget {
   plugins: WidgetPlugin[] = []
+  pos: Ref<Position>
   x: Ref<number> // The vector x of the widget.
   y: Ref<number> // The vector y of the widget.
   centerX: Ref<number> // The center vector x of the widget.
@@ -61,7 +66,7 @@ export class Widget {
     .slice(2)}`
 
   parent: Widget | null
-  private status: Status = 'unborn'
+  status: Status = 'unborn'
   initialized: boolean = false
 
   registeredEvents: Map<string, Event<Widget>> = new Map()
@@ -70,6 +75,7 @@ export class Widget {
     options ??= {}
     this.x = ref(options.x ?? 0)
     this.y = ref(options.y ?? 0)
+    this.pos = ref(rp(this.x.value, this.y.value))
     this.centerX = ref(options.centerX ?? 0)
     this.centerY = ref(options.centerY ?? 0)
     this.progress = ref(options.progress ?? 1)
@@ -102,7 +108,16 @@ export class Widget {
    * Called when the widget is registered.
    * @param _ck The CanvasKit namespace
    */
-  init(_ck: CanvasKit) {}
+  init(_ck: CanvasKit) {
+    changed(this.pos, (pos) => {
+      if (this.parent instanceof RootWidget) {
+        [this.x.value, this.y.value] = pos.value.resolve(...this.parent.canvasSize)
+      }
+      else {
+        [this.x.value, this.y.value] = pos.value.resolve(this.parent.x.value, this.y.value)
+      }
+    })
+  }
 
   /**
    * Draw the object according to the parameters of the widget.
@@ -116,7 +131,11 @@ export class Widget {
    * Called when the style is changed.
    * @param canvas The canvas object of CanvasKit-WASM.
    */
-  update(elapsed: number, ck: CanvasKit, canvas: Canvas, app: App) {
+  update(
+    elapsed: number,
+    ck: CanvasKit,
+    canvas: Canvas,
+  ) {
     if (!this.initialized) {
       this.init(ck)
       this.initialized = true
@@ -141,7 +160,7 @@ export class Widget {
       }
     }
     for (const child of this.children) {
-      child.update(elapsed, ck, canvas, app)
+      child.update(elapsed, ck, canvas)
     }
 
     canvas.restore()