gradient_border/styles.css

 *
 {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: consolas;
 }       
 body
 {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #111;
 }
 .container
 {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 40px 0;
    flex-wrap: wrap;
 }
 .container .box
 {
    position: relative;
    width: 320px;
    height: 400px;
    color: #fff;
    background: #111;
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 20px 30px;
    transition: 0.5s;
 }
 .container .box:hover
 {
    transform: translateY(-20px);
 }
 .container .box::before
 {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;  
  background: linear-gradient(45deg,#ffbc00,#ff0058);
 }
 .container .box::after
 {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;  
  background: linear-gradient(45deg,#ffbc00,#ff0058);
  filter: blur(30px);
 }
 .container .box:nth-child(2)::before,
 .container .box:nth-child(2)::after
 {
    background: linear-gradient(315deg,#03a9f4,#ff0058);
 }
 .container .box:nth-child(3)::before,
 .container .box:nth-child(3)::after
 {
    background: linear-gradient(315deg,#4dff03,#00d0ff);
 }
 .container .box span
 {
    position: absolute;
    top: 6px;
    left: 6px;
    right: 6px;
    bottom: 6px;
    background: rgba(0,0,0,0.6);
    z-index: 2;
 }
 .container .box span::before
 {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 50%;
    height: 100%;
    background: rgba(255,255,255,0.1);
    pointer-events: none;
 }
 .container .box .content
 {
    z-index: 10;
    padding: 20px 40px;
 }
 .container .box .content h2
 {
    font-size: 2em;
    color: #fff;
    margin-bottom: 10px;
 }
 .container .box .content p
 {
    font-size: 1.1em;
    color: #fff;
    margin-bottom: 10px;
    line-height: 1.4em; 
}
.container .box .content a
{
    display: inline-block;
    font-size: 1.1em;
    color: #111;
    background: #fff;
    padding: 10px;
    text-decoration: none;
    font-weight: 700;
}