body {
  background-color: gray;
}

h1 {
  color: black;
}

div {
  padding: 3vw;
  margin: 3vw;
}

button {
  background-color: rgb(115, 115, 115);
  border-color: rgb(128,128,128);
  width: 6vmax;
  font-size: 1vmax;
  display: inline-block;
  transition: background-color 0.5s
}

button:hover {
  background-color: rgb(166,166,166)
}

a {
  transition: font-size 1s
}

a:hover {
  font-size: 20px
}

.visible {
  border-width: 3px;
  border-color: black;
  border-style: solid
}

.clearfix {
  overflow: auto;
}