style.css

* {
  padding: 0;
  box-sizing: border-box;
  font-family: "sans";
}

@font-face {
  font-family: "sans";
  src: url(font/sans.ttf);
}

body {
  overflow: hidden;
  background: #19172e;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

footer, a {
  color: #fff;
}

h1 {
  color: #fff;
  text-align: center;
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  padding-top: 10px;
}

.key {
  border: 1px solid #999;
  background-color: #eee;
  box-shadow: 1px 1px 3px rgba(0, 0, 0, 0.1);
  display: inline-flex;
  align-items: center;
  font-size: 20px;
  font-weight: bold;
  padding: 20px;
  flex-direction: column;
  margin: 10px;
  min-width: 150px;
  position: relative;
}

.key small {
  position: absolute;
  top: -24px;
  left: 0;
  text-align: center;
  width: 100%;
  color: rgb(194, 178, 178);
  font-size: 14px;
}

@media(max-width:768px){
 .key{
   margin: 10px 0px;
  }
}

footer {
  text-align: center;
  position: absolute;
  bottom: 0;
}