HTMLify

* {
  box-sizing: border-box;
}

body {
  height: 100vh;
  font-family: sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
  overflow: hidden;
  margin: 0;
  background: linear-gradient(blueviolet, rgb(79, 21, 134));
}

#insert {
  background: white;
  padding: 50px;
}

.key {
  border: 2px solid #ccc;
  background-color: rgba(137, 43, 226, 0.767);
  border: none;
  color: white;
  display: inline-flex;
  align-content: center;
  font-size: 20px;
  font-weight: bold;
  padding: 20px;
  flex-direction: column;
  margin: 10px;
  min-width: 150px;
  position: relative;
}

/* JavaScript */
.key small {
  position: absolute;
  top: -24px;
  left: 0;
  text-align: center;
  width: 100%;
  color: #555;
  font-size: 14px;
}