* {
  font-family: system-ui, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  box-sizing: border-box;
}
body {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
}
.glow-button {
  padding: 15px 30px;
  border: none;
  outline: none;
  color: white;
  background: #2c3e50;
  cursor: pointer;
  position: relative;
  z-index: 0;
  border-radius: 10px;
  font-size: 16px;
  font-weight: 500;
}
.glow-button:before {
  content: '';
  background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
  position: absolute;
  top: -2px;
  left:-2px;
  background-size: 400%;
  z-index: -1;
  filter: blur(5px);
  width: calc(100% + 4px);
  height: calc(100% + 4px);
  animation: glowing 20s linear infinite;
  opacity: 0;
  transition: opacity .3s ease-in-out;
  border-radius: 10px;
}
.glow-button:hover:before {
  opacity: 1;
}
.glow-button:after {
  z-index: -1;
  content: '';
  position: absolute;
  width: 100%;
  height: 100%;
  background: #2c3e50;
  left: 0;
  top: 0;
  border-radius: 10px;
}
@keyframes glowing {
  0% { background-position: 0 0; }
  50% { background-position: 400% 0; }
  100% { background-position: 0 0; }
}