<div class="danmu"> <marquee behavior="scroll" direction="left" scrollamount="30"><font color="red" size="15px" >树枝666</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="20"><font color="aqua" size="20px">你干嘛~哎呦</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="25"><font >油饼食不食</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="20"><font color="pink" size="10px">贞德士泥鸭</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="28"><font color="red">amagi</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="20"><font color="greenyellow" size="20px">蒸虾头</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="10"><font size="16px" >荔枝，你要我拿什么荔枝</font> </marquee> <marquee behavior="scroll" direction="left" scrollamount="15"><font color="pink" size="20px">激尼钛霉</font> </marquee> </div>这段代码如何增加一个用户输入功能

你可以使用HTML的`<input>`标签来实现用户输入功能，例如：

<div class="danmu">
    <marquee behavior="scroll" direction="left" scrollamount="30"><font color="red" size="15px" >树枝666</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="20"><font color="aqua" size="20px">你干嘛~哎呦</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="25"><font>油饼食不食</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="20"><font color="pink" size="10px">贞德士泥鸭</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="28"><font color="red">amagi</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="20"><font color="greenyellow" size="20px">蒸虾头</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="10"><font size="16px" >荔枝，你要我拿什么荔枝</font></marquee>
    <marquee behavior="scroll" direction="left" scrollamount="15"><font color="pink" size="20px">激尼钛霉</font></marquee>
    <input type="text" placeholder="请输入弹幕内容" onkeydown="if(event.keyCode==13){sendDanmu();}">
</div>

这里使用了`<input>`标签，并设置了`type="text"`，表示输入框是一个文本输入框。同时，还设置了`placeholder`属性来提示用户输入内容。在输入框中按下回车键时，调用了一个JavaScript函数`sendDanmu()`，这个函数需要你自己编写，用来将用户输入的内容添加到弹幕中。