diff --git a/package.json b/package.json
index 2c1d834a..189216c6 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "boot-cell",
-    "version": "2.0.0-beta.11",
+    "version": "2.0.0-beta.12",
     "license": "LGPL-3.0",
     "author": "shiy2008@gmail.com",
     "description": "Web Components UI library based on WebCell v3, BootStrap v5, BootStrap Icon v1 & FontAwesome v6",
diff --git a/v1/Calendar/CountDown/index.tsx b/source/CountDown.tsx
similarity index 73%
rename from v1/Calendar/CountDown/index.tsx
rename to source/CountDown.tsx
index 9823c431..982cf732 100644
--- a/v1/Calendar/CountDown/index.tsx
+++ b/source/CountDown.tsx
@@ -1,14 +1,7 @@
-import {
-    WebCellProps,
-    component,
-    mixin,
-    attribute,
-    watch,
-    createCell
-} from 'web-cell';
-
-import { Status } from '../../utility/constant';
-import style from './index.less';
+import { computed, observable } from 'mobx';
+import { WebCell, attribute, component, observer } from 'web-cell';
+
+import { Status } from './type';
 
 interface TimeUnit {
     scale: number;
@@ -22,24 +15,24 @@ interface TimeSection {
 
 const colors = Object.keys(Status).slice(0, 4);
 
-export interface CountDownProps extends WebCellProps {
+export interface CountDownProps {
     endTime?: string | Date | number;
 }
 
-@component({
-    tagName: 'count-down',
-    renderTarget: 'children'
-})
-export class CountDown extends mixin<CountDownProps>() {
+export interface CountDown extends WebCell<CountDownProps> {}
+
+@component({ tagName: 'count-down' })
+@observer
+export class CountDown extends HTMLElement implements WebCell<CountDownProps> {
     @attribute
-    @watch
-    endTime: CountDownProps['endTime'] = Date.now();
+    @observable
+    accessor endTime: CountDownProps['endTime'] = Date.now();
 
-    @watch
-    rest = 0;
+    @observable
+    accessor rest = 0;
 
-    @watch
-    units: TimeUnit[] = [
+    @observable
+    accessor units: TimeUnit[] = [
         {
             scale: 24,
             label: 'D'
@@ -58,6 +51,7 @@ export class CountDown extends mixin<CountDownProps>() {
         }
     ];
 
+    @computed
     get timeSections() {
         var { rest } = this;
 
@@ -105,7 +99,9 @@ export class CountDown extends mixin<CountDownProps>() {
             <ol className="list-inline text-white">
                 {this.timeSections.map(({ value, label }, index) => (
                     <li
-                        className={`list-inline-item display-4 bg-${colors[index]} ${style.section}`}
+                        key={value}
+                        className={`list-inline-item display-4 bg-${colors[index]} d-inline-flex align-items-center justify-content-center rounded-5`}
+                        style={{ width: '5.5rem', height: '5.5rem' }}
                     >
                         <small>
                             {(value + '').padStart(2, '0')}
diff --git a/source/index.ts b/source/index.ts
index 2ac23f46..7f9a9c68 100644
--- a/source/index.ts
+++ b/source/index.ts
@@ -19,4 +19,5 @@ export * from './Carousel';
 export * from './Nav';
 export * from './Navbar';
 export * from './Offcanvas';
+export * from './CountDown';
 export * from './MonthCalendar';
diff --git a/v1/Calendar/CountDown/index.less b/v1/Calendar/CountDown/index.less
deleted file mode 100644
index ec596de2..00000000
--- a/v1/Calendar/CountDown/index.less
+++ /dev/null
@@ -1,8 +0,0 @@
-.section {
-    display: inline-flex;
-    align-items: center;
-    justify-content: center;
-    width: 5.5rem;
-    height: 5.5rem;
-    border-radius: 10px;
-}