diff --git a/src/Common.js b/src/Common.js
index ddd0a38..a282400 100644
--- a/src/Common.js
+++ b/src/Common.js
@@ -9,6 +9,8 @@ import './Common.css';
 
 const chinese_format=buildFormatter(chineseStrings);
 
+export const API_BASE=window.location.protocol==='https:' ? '/api_proxy' : 'http://www.pkuhelper.com/services/pkuhole';
+
 const PID_RE=/(^|[^\d])([1-9]\d{4,5})(?!\d)/g;
 const NICKNAME_RE=/(^|[^A-Za-z])((?:(?:Angry|Baby|Crazy|Diligent|Excited|Fat|Greedy|Hungry|Interesting|Japanese|Kind|Little|Magic|Naïve|Old|Powerful|Quiet|Rich|Superman|THU|Undefined|Valuable|Wifeless|Xiangbuchulai|Young|Zombie)\s)?(?:Alice|Bob|Carol|Dave|Eve|Francis|Grace|Hans|Isabella|Jason|Kate|Louis|Margaret|Nathan|Olivia|Paul|Queen|Richard|Susan|Thomas|Uma|Vivian|Winnie|Xander|Yasmine|Zach)|You Win|洞主)(?![A-Za-z])/gi;
 
@@ -54,3 +56,42 @@ export class HighlightedText extends PureComponent {
         )
     }
 }
+
+window.TEXTAREA_BACKUP={};
+
+export class SafeTextarea extends Component {
+    constructor(props) {
+        super(props);
+        this.state={
+            text: window.TEXTAREA_BACKUP[props.id]||'',
+        };
+        this.on_change_bound=this.on_change.bind(this);
+        this.clear=this.clear.bind(this);
+        this.area_ref=React.createRef();
+        this.change_callback=props.on_change;
+    }
+
+    componentWillUnmount() {
+        window.TEXTAREA_BACKUP[this.props.id]=this.state.text;
+        this.change_callback(this.state.text);
+    }
+
+    on_change(event) {
+        this.setState({
+            text: event.target.value,
+        });
+        this.change_callback(event.target.value);
+    }
+
+    clear() {
+        this.setState({
+            text: '',
+        });
+    }
+
+    render() {
+        return (
+            <textarea ref={this.area_ref} onChange={this.on_change_bound} value={this.state.text} />
+        )
+    }
+}
\ No newline at end of file
diff --git a/src/Flows.css b/src/Flows.css
index 5c59a70..0222f48 100644
--- a/src/Flows.css
+++ b/src/Flows.css
@@ -97,11 +97,13 @@
 .flow-item-row p.img {
     text-align: center;
 }
-p.img img {
+.flow-item-row p.img img {
     max-width: 100%;
-    max-height: 100vh;
     box-shadow: 0 1px 5px rgba(0,0,0,.4);
 }
+.left-container .flow-item-row p.img img {
+    max-height: 80vh;
+}
 
 .box-header-badge {
     float: right;
diff --git a/src/Flows.js b/src/Flows.js
index b023a20..def2c0b 100644
--- a/src/Flows.js
+++ b/src/Flows.js
@@ -1,14 +1,14 @@
 import React, {Component, PureComponent} from 'react';
 import {ColorPicker} from './color_picker';
-import {Time, TitleLine, HighlightedText} from './Common.js';
+import {Time, TitleLine, HighlightedText} from './Common';
 import './Flows.css';
 import LazyLoad from 'react-lazyload';
-import {AudioWidget} from './AudioWidget.js';
-import {TokenCtx} from './UserAction';
+import {AudioWidget} from './AudioWidget';
+import {TokenCtx, ReplyForm} from './UserAction';
 
+import {API_BASE} from './Common';
 const IMAGE_BASE='http://www.pkuhelper.com/services/pkuhole/images/';
 const AUDIO_BASE='/audio_proxy/';
-const API_BASE=window.location.protocol==='https:' ? '/api_proxy' : 'http://www.pkuhelper.com/services/pkuhole';
 
 const SEARCH_PAGESIZE=50;
 const CLICKABLE_TAGS={a: true, audio: true};
@@ -145,15 +145,17 @@ class FlowItemRow extends PureComponent {
             });
     }
 
+    reload_sidebar() {
+        this.props.show_sidebar('帖子详情',<p className="box box-tip">加载中……</p>);
+        this.load_replies(this.show_sidebar.bind(this));
+    }
+
     show_sidebar() {
         this.props.show_sidebar(
             '帖子详情',
             <div className="flow-item-row sidebar-flow-item">
                 <div className="box box-tip">
-                    <a onClick={()=>{
-                        this.props.show_sidebar('帖子详情',<p className="box box-tip">加载中……</p>);
-                        this.load_replies(this.show_sidebar.bind(this));
-                    }}>刷新回复</a>
+                    <a onClick={this.reload_sidebar.bind(this)}>刷新回复</a>
                     {this.props.token &&
                         <span>
                             &nbsp;/&nbsp;
@@ -175,6 +177,9 @@ class FlowItemRow extends PureComponent {
                         <Reply info={reply} color_picker={this.color_picker} />
                     </LazyLoad>
                 ))}
+                {this.props.token &&
+                    <ReplyForm pid={this.state.info.pid} token={this.props.token} on_complete={this.reload_sidebar.bind(this)} />
+                }
             </div>
         );
     }
diff --git a/src/Title.js b/src/Title.js
index 725f06b..671de7f 100644
--- a/src/Title.js
+++ b/src/Title.js
@@ -12,7 +12,7 @@ const HELP_TEXT=(
             <li>在列表中点击帖子可以展开全部回复</li>
             <li>在搜索框输入 #472865 等可以查看指定 ID 的树洞</li>
             <li>新的帖子会在左上角显示一个圆点</li>
-            <li>登录后可以关注帖子</li>
+            <li>本网站支持 3D Touch，重压屏幕可以快速返回 / 刷新树洞</li>
             <li>请注意：使用 HTTPS 访问本站可能会<b>大幅减慢</b>加载速度</li>
             <li>自定义背景图片请修改 <code>localStorage['REPLACE_ERIRI_WITH_URL']</code></li>
         </ul>
diff --git a/src/UserAction.css b/src/UserAction.css
index 09b7e93..b594a44 100644
--- a/src/UserAction.css
+++ b/src/UserAction.css
@@ -5,4 +5,17 @@
 
 .login-form button {
     min-width: 100px;
+}
+
+.reply-form {
+    display: flex;
+}
+.reply-form textarea {
+    resize: vertical;
+    flex: 1;
+    min-height: 3em;
+    height: 5em;
+}
+.reply-form button {
+    flex: 0 0 50px;
 }
\ No newline at end of file
diff --git a/src/UserAction.js b/src/UserAction.js
index 885c036..709555f 100644
--- a/src/UserAction.js
+++ b/src/UserAction.js
@@ -1,7 +1,9 @@
 import React, {Component, PureComponent} from 'react';
+import {SafeTextarea} from './Common';
 
 import './UserAction.css';
 
+import {API_BASE} from './Common';
 const LOGIN_BASE=window.location.protocol==='https:' ? '/login_proxy' : 'http://www.pkuhelper.com/services/login';
 
 export const TokenCtx=React.createContext({
@@ -63,7 +65,10 @@ export class LoginForm extends Component {
             <TokenCtx.Consumer>{(token)=>
                 <div className="login-form">
                     <form onSubmit={(e)=>this.do_login(e,token.set_value)} className="box">
-                        <p>Token: <code>{token.value||'(null)'}</code></p>
+                        <p>{token.value ?
+                            <span><b>您已登录。</b>Token: <code>{token.value||'(null)'}</code></span> :
+                            '登录后可以使用关注、回复等功能'
+                        }</p>
                         <p>
                             <label>
                                 学号：
@@ -95,4 +100,79 @@ export class LoginForm extends Component {
             }</TokenCtx.Consumer>
         )
     }
+}
+
+export class ReplyForm extends Component {
+    constructor(props) {
+        super(props);
+        this.state={
+            text: '',
+            loading_status: 'done',
+        };
+        this.on_change_bound=this.on_change.bind(this);
+        this.area_ref=React.createRef();
+    }
+
+    on_change(value) {
+        this.setState({
+            text: value,
+        });
+    }
+
+    on_submit(event) {
+        event.preventDefault();
+
+        if(this.state.loading_status==='loading')
+            return;
+        this.setState({
+            loading_status: 'loading',
+        });
+
+        let data=new URLSearchParams();
+        data.append('action','docomment');
+        data.append('pid',this.props.pid);
+        data.append('text',this.state.text);
+        data.append('token',this.props.token);
+        fetch(API_BASE+'/api.php', {
+            method: 'POST',
+            headers: {
+                'Content-Type': 'application/x-www-form-urlencoded',
+            },
+            body: data,
+        })
+            .then((res)=>res.json())
+            .then((json)=>{
+                if(json.code!==0)
+                    throw new Error(json);
+
+                this.setState({
+                    loading_status: 'done',
+                    text: '',
+                });
+                this.area_ref.current.clear();
+                this.props.on_complete();
+            })
+            .catch((e)=>{
+                console.trace(e);
+                alert('回复失败\n（树洞服务器经常抽风，其实有可能已经回复上了，不妨点“刷新回复”看一看）');
+                this.setState({
+                    loading_status: 'done',
+                });
+            });
+    }
+
+    render() {
+        return (
+            <div className="box">
+                <form onSubmit={this.on_submit.bind(this)} className="reply-form">
+                    <SafeTextarea ref={this.area_ref} id={this.props.pid} on_change={this.on_change_bound} />
+                    {this.state.loading_status==='loading' ?
+                        <button disabled="disabled">正在回复……</button> :
+                        <button type="submit">回复</button>
+                    }
+
+                </form>
+            </div>
+        )
+    }
 }
\ No newline at end of file
diff --git a/src/index.css b/src/index.css
index 97ae885..432d015 100644
--- a/src/index.css
+++ b/src/index.css
@@ -1,7 +1,6 @@
 body {
     margin: 0;
     padding: 0;
-    font-family: '微软雅黑', 'Microsoft YaHei', sans-serif;
     background-size: cover;
     overflow-x: hidden;
 }
@@ -10,6 +9,10 @@ body::-webkit-scrollbar {
     display: none;
 }
 
+body, textarea, pre {
+    font-family: '微软雅黑', 'Microsoft YaHei', sans-serif;
+}
+
 * {
     box-sizing: border-box;
     word-wrap: break-word;
@@ -26,11 +29,13 @@ a {
     cursor: pointer;
 }
 
-input {
-    padding: 0 1em;
+input, textarea {
     border-radius: 5px;
     border: 1px solid black;
     outline: none;
+}
+input {
+    padding: 0 1em;
     line-height: 2em;
 }
 
@@ -40,7 +45,6 @@ audio {
 
 pre {
     white-space: pre-wrap;
-    font-family: '微软雅黑', 'Microsoft YaHei', sans-serif;
 }
 
 button, .button {