Underline Draw Input

<!--
  Author: @emma-lake
  License: MIT
  Tags: #buttons #css #interface #opensource #codepeek
-->
<div class="draw-input">
  <input type="text" class="draw-input__field" placeholder="Your email address" />
  <span class="draw-input__underline"></span>
</div>

/*
 * Author: @emma-lake
 * License: MIT
 * Tags: #buttons #css #interface #opensource #codepeek
 */

.draw-input {
  position: relative;
  width: 260px;
}
.draw-input__field {
  width: 100%;
  border: none;
  outline: none;
  background: transparent;
  padding: 10px 2px 12px;
  font-family: system-ui, sans-serif;
  font-size: 15px;
  color: #f1f1f1;
  border-bottom: 1px solid #2c2c35;
}
.draw-input__field::placeholder {
  color: #6b6b76;
}
.draw-input__underline {
  position: absolute;
  left: 50%;
  bottom: 0;
  width: 42%;
  height: 2px;
  transform: translateX(-50%);
  background: linear-gradient(90deg, transparent, #f59e0b, #ef4444, #f59e0b, transparent);
  background-size: 300% 100%;
  opacity: 0.55;
  border-radius: 2px;
  animation: draw-underline-idle 3.2s linear infinite;
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.4s ease;
}
.draw-input__field:focus ~ .draw-input__underline {
  width: 100%;
  opacity: 1;
  box-shadow: 0 0 12px -2px rgba(239, 68, 68, 0.6);
}
@keyframes draw-underline-idle {
  0% { background-position: 0% 0; }
  100% { background-position: 300% 0; }
}