Glowing Border. Делаем красивый border у блока CSS, HTML

@import url('https://fonts.googleapis.com/css?family=Poppins:100,200,300,400,500,600,700,800,900');
body {
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #060c21;
  font-family: 'Poppins', sans-serif;
}
.box {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #060c21;
  max-width: 300px;
}
.box::before {
  content: '';
  position: absolute;
  top: -2px;
  left: -2px;
  right: -2px;
  bottom: -2px;
  background: #fff;
  z-index: -1;
}
.box::after {
  content: '';
  position: absolute;
  top: -2px;
  left: -2px;
  right: -2px;
  bottom: -2px;
  background: #fff;
  z-index: -2;
  filter: blur(40px);
}
.box::before,
.box::after {
  background: linear-gradient(235deg, #89ff00, #060c21, #00bcd4);
}
.content {
  padding: 20px;
  box-sizing: border-box;
  color: #ffffff;
}