diff --git a/demo/24-patch.html b/demo/24-patch.html
new file mode 100644
index 0000000..c3b5eca
--- /dev/null
+++ b/demo/24-patch.html
@@ -0,0 +1,127 @@
+<style>
+.red { color: red; }
+.green { color: green; }
+</style>
+    
+<body>
+  <div id="app"></div>
+</body>
+    
+<script>
+function h(tag, props, children) {
+  return {
+    tag,
+    props,
+    children,
+  }
+}
+
+function mount(vnode, container) {
+  const el = vnode.el = document.createElement(vnode.tag);
+  vnode.parent = container
+  // handle props
+  if (vnode.props) {
+    for (let key in vnode.props) {
+        if (key.startsWith('on')) { // 事件绑定
+        const eventName = key.slice(2).toLowerCase();
+        el.addEventListener(eventName, vnode.props[key]);
+      } else {
+        el.setAttribute(key, vnode.props[key]);
+      }
+    }
+  }
+  // handle children
+  if (vnode.children) {
+    if (Array.isArray(vnode.children)) {
+      vnode.children.forEach(child => {
+        mount(child, el);
+      });
+    } else { // text node
+      el.textContent = vnode.children;
+    }
+  }
+
+  container.appendChild(el);
+}
+
+const vdom = h('div', { class: 'red' }, [
+  h('span', null, 'hello')
+])
+
+mount(vdom, document.getElementById('app'))
+
+function patch(n1, n2) {
+  // there are lots of assumption and only handle simpler cases
+
+  // patch tag
+  if (n1.tag === n2.tag) {
+    const el = n1.el
+    // patch props
+    const oldProps = n1.props || {}
+    const nweProps = n2.props || {}
+    for (const key in nweProps) {
+      const oldValue = oldProps[key]
+      const newValue = nweProps[key]
+      if (oldValue !== newValue) {
+        el.setAttribute(key, newValue)
+      }
+    }
+    // patch children
+    const oldChildren = n1.children
+    const newChildren = n2.children
+    if (typeof newChildren === 'string') {
+      if (typeof oldChildren === 'string') {
+        if (newChildren !== oldChildren) {
+          el.textContent = newChildren
+        }
+      } else { 
+        // oldChildren is a array, but we can just override it
+        el.textContent = newChildren
+      }
+    } else {
+      if (typeof oldChildren === 'string') {
+        // discard oldChildren
+        el.innerHTML = ''
+        // mount newChildren
+        newChildren.forEach(child => {
+          mount(child, el)
+        })
+      } else {
+        // both old and new is a array
+
+        const commonLength = Math.min(oldChildren.length, newChildren.length)
+        for (let i = 0; i < commonLength; i++) {
+          patch(oldChildren[i], newChildren[i])
+        }
+        if (newChildren.length > oldChildren.length) {
+          // to new node, just mount it 
+          newChildren.slice(oldChildren.length).forEach(child => {
+            mount(child, el)
+          })
+        } else if (newChildren.length < oldChildren.length) {
+          oldChildren.slice(newChildren.length).forEach(child => {
+            // unmount old el
+            el.removeChild(child.el)
+          })
+        }
+      }
+    }
+  } else {
+    // ... replace
+
+    // unmount old dom
+    n1.parent.removeChild(n1.el)
+    // mount new dom
+    mount(n2, n1.parent)
+  }
+}
+
+const vdom2 = h('div', { class: 'green' }, [
+  h('span', null, 'changed!')
+])
+
+setTimeout(() => {
+  patch(vdom, vdom2)
+}, 1000)
+
+</script>
\ No newline at end of file
diff --git a/demo/23-counter.html b/demo/25-counter.html
similarity index 100%
rename from demo/23-counter.html
rename to demo/25-counter.html
diff --git a/demo/24-counter-using-render-function-options.html b/demo/26-counter-using-render-function-options.html
similarity index 100%
rename from demo/24-counter-using-render-function-options.html
rename to demo/26-counter-using-render-function-options.html
diff --git a/public/patch.excalidraw.png b/public/patch.excalidraw.png
index 151bb33..7fd485b 100644
Binary files a/public/patch.excalidraw.png and b/public/patch.excalidraw.png differ
diff --git a/slides.md b/slides.md
index c6a2aec..2769f77 100644
--- a/slides.md
+++ b/slides.md
@@ -1351,7 +1351,7 @@ const ast = {
 }
 ```
 
-定义节点类型:
+定义节点类型枚举:
 
 ```js
 const NodeTypes = {
@@ -2415,9 +2415,36 @@ createApp({
 
 ---
 
+`patch` 函数的实现如下:
+
+```js
+/**
+ * @param {*} n1 old vnode
+ * @param {*} n2 new vnode
+ */
+function patch(n1, n2) {
+  if (n1.tag === n2.tag) {
+    // ...
+  } else {
+    // ...
+  }
+}
+```
+
+具体代码和demo见: `24-patch.html`
+
+---
+
+现在，我们已经实现了 **挂载** 和 **更新**，整合之前的代码，接下来再来看下 **计数器** demo 的效果。
+
+---
+
 ## Counter 计数器
 
-demo: `22-counter.html`
+demo: `25-counter.html`
+
+> 打开 DevTools 的 Elements 查看效果
+
 
 <div grid="~ cols-2 gap-2">
 
@@ -2497,9 +2524,9 @@ function createApp(options = {}) {
 <div id="app"></div>
 ```
 
-```html
-<script>
-// demo: 24-render-function-options.html
+```js
+// demo: 26-render-function-options.html
+
 const { createApp, ref, h } = MiniVue
 createApp({
   setup() {
@@ -2521,7 +2548,6 @@ createApp({
     ])
   }
 }).mount('#app')
-</script>
 ```
 
 </div>
