Create a menu with a curtain falling animation using CSS and JavaScript

https://yogeshchauhan.com/create-a-menu-with-a-curtain-falling-animation-using-css-and-javascript/

by velo_ninja

HTML

<button id="menu-button-open">
  MENU
</button>

<section id="menu" class="hide">
  <button id="menu-button-close">
    CLOSE
  </button>
  <ul>
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
    <li>Item 4</li>
    <li>Item 5</li>
  </ul>
</section>

<br><br><br>

<p class="blog">
This fiddle is a part of a <a href="https://yogeshchauhan.com/create-a-menu-with-a-curtain-falling-animation-using-css-and-javascript/" target="_blank">Blog Post on YogeshChauhan.com</a>
</p>

SCSS

#menu-button-open,
#menu-button-close {
  margin: 1rem;
  padding: 1rem;
  background-color: green;
  outline: none;
  border: none;
  cursor: pointer;
  color: white;
}

#menu {
  display: none;
  position: absolute;
  top: 0;
  z-index: 1;
  transform-origin: top center;
  animation: curtain 1.5s;
  animation-direction: forwards;
  background: orange;
  height: 100%;
  width: 100%;
  transition: all 1s ease-in;

  ul {
    display: flex;
    flex-direction: column;

    li {
      background: blue;
      padding: 0.9rem;
      margin: 0.7rem;
      list-style: none;
    }
  }
}

@keyframes curtain {
  0% {
    transform: perspective(25rem) rotateX(-90deg);
    opacity: 1;
  }

  25% {
    transform: perspective(25rem) rotateX(25deg);
  }

  55% {
    transform: perspective(25rem) rotateX(-9deg);
  }

  100% {
    transform: perspective(25rem) rotateX(0deg);
  }
}

body {
  margin: 0;
  background: #444;
  min-height: 200px;
  color: ghostwhite;
}

.blog {
  color: white;
  position: absolute;
  bottom: 5rem;
  z-index: 2;

  a {
    color: white;
  }
}

JavaScript

const menu = document.getElementById("menu");

document.getElementById("menu-button-open").addEventListener("click", function() {
  menu.style.display = "block";
});

document.getElementById("menu-button-close").addEventListener("click", function() {
  menu.style.display = "none";
});