Button shape and button event

I want to create a triangular border button that contains an exclamation point.
I hope this button disappears when the button is clicked.
This is my code at the moment. I do not know what to do.

.triangle {
     width: 50px;
   height: 50px;
   border: 1px solid red;
   border-radius: 10px;
   background-color: white;

<table style="margin: 7px" layout="column" layout-align="start start">
 <th  class="table" >clear</th>
  <tr style="text-align: center">
    <td><form><input type=submit value="!" class="triangle"></form></td>
  1. What version of NR, node.js and node-red-dashbord? (all 3 can be found in the log at startup)

  2. What node are you putting that code in?

  3. if the node shows what happens when you click it?

  4. do you want the entire button or the exclimation point to disappear?

You can use onClick() method in button, you not pass an handleSubmit() on form?