Elastic Morph Send Button

<!--
  Author: @codepeek
  License: MIT
  Tags: #buttons #css #interface #opensource #codepeek
-->
<button class="morph-btn" onclick="this.classList.toggle('is-loading')">
  <span class="morph-btn__text">Send Message</span>
  <span class="morph-btn__spinner"></span>
  <span class="morph-btn__check">✓</span>
</button>

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

.morph-btn {
  position: relative;
  width: 160px;
  height: 48px;
  border: none;
  border-radius: 24px;
  background: linear-gradient(135deg, #6366f1, #8b5cf6);
  color: #ffffff;
  font-family: system-ui, sans-serif;
  font-weight: 600;
  font-size: 15px;
  cursor: pointer;
  overflow: hidden;
  box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1), background 0.3s ease, border-radius 0.4s ease;
}
.morph-btn:hover {
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.6);
  transform: translateY(-1px);
}
.morph-btn__text {
  display: block;
  transition: opacity 0.2s ease, transform 0.2s ease;
}
.morph-btn__spinner {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 22px;
  height: 22px;
  margin: -11px;
  border: 3px solid rgba(255,255,255,0.3);
  border-top-color: #fff;
  border-radius: 50%;
  opacity: 0;
  animation: spin 0.8s linear infinite;
}
.morph-btn__check {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0);
  font-size: 20px;
  opacity: 0;
  transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275), opacity 0.2s;
}
.morph-btn.is-loading {
  width: 48px;
  border-radius: 50%;
}
.morph-btn.is-loading .morph-btn__text {
  opacity: 0;
  transform: translateY(-10px);
}
.morph-btn.is-loading .morph-btn__spinner {
  opacity: 1;
}