Why toggle is not working if I don’t add CSS? – Blancer.com Tutorials and projects

I am an absolute beginner. I am trying to do this project on animated search bar where it toggles between buttons.

Before adding CSS, I was trying to click on the icons to toggle but it didn’t work. Then I added CSS and it is working just fine. I thought CSS is for styling HTML documents.

What am I not understanding here? Does toggling work when 2 icons are together, overlapping or something. Can someone explain what is going on?

Code Snippet
(GitHub Source)

const searchBarContainerEl = document.querySelector(".search-bar-container");

const magnifierEl = document.querySelector(".magnifier");

magnifierEl.addEventListener("click", () => {
  searchBarContainerEl.classList.toggle("active");
});

body {
  margin: 0;
  display: flex;
  justify-content: center;
  height: 100vh;
  align-items: center;
  background-color: aliceblue;
}

.search-bar-container {
  display: flex;
  align-items: center;
  background-color: aliceblue;
  padding: 5px;
  width: 300px;
  height: 50px;
  border-radius: 50px;
  box-shadow: 6px 6px 10px rgba(0, 0, 0, 0.2), -6px -6px 10px rgba(255, 255, 255, 0.7);
  margin: 10px;
  position: relative;
  transition: width 1.5s;
}

.magnifier {
  width: 25px;
  cursor: pointer;
  position: absolute;
  left: 20px;
}

.mic-icon {
  width: 30px;
  position: absolute;
  right: 10px;
  transition: width 0.4s;
  transition-delay: 1s;
}

.input {
  background-color: transparent;
  border: none;
  margin: 10px 50px;
  width: 100%;
  outline: none;
  color: rgb(100, 100, 100);
  transition: width 1s;
  transition-delay: 0.5s;
}

.active.search-bar-container {
  width: 50px;
}

.active .input {
  width: 0;
}

.active .mic-icon {
  width: 0;
}

<div class="search-bar-container active">
  <img src="https://cdn4.iconfinder.com/data/icons/evil-icons-user-interface/64/magnifier-512.png" alt="magnifier" class="magnifier" />
  <input type="text" class="input" placeholder="Search ..." />
  <img src="https://cdn1.iconfinder.com/data/icons/google-s-logo/150/Google_Icons-25-512.png" alt="mic-icon" class="mic-icon" />
</div>