body {
  background: linear-gradient(rgb(0, 225, 255), rgb(79, 255, 79)) no-repeat
    center center fixed;
}
.calculator,
.display,
.buttons {
  border: 2px solid black;
  padding: 10px 5px;
}
.calculator {
  margin: 80px auto 30px;
  max-width: 350px;
  background: rgb(51, 51, 51);
  border-radius: 5px;
  padding: 10px;
  box-shadow: 5px 5px 5px black;
}
.display {
  background: black;
  text-align: right;
  border-radius: 5px 5px 0 0;
  padding: 5px;
}
.formula {
  color: rgb(255, 136, 0);
  font-size: 16px;
  margin: 0;
  line-height: 15px;
  border-top: 1px solid grey;
  border-left: 1px solid grey;
  border-right: 1px solid grey;
  border-radius: 4px 4px 0 0;
  padding: 3px 5px 0;
  min-height: 19px;
}
.output {
  color: rgb(0, 206, 0);
  font-size: larger;
  margin: 0;
  line-height: 25px;
  border-bottom: 1px solid grey;
  border-left: 1px solid grey;
  border-right: 1px solid grey;
  border-radius: 0 0 4px 4px;
  padding: 0 5px 3px;
  min-height: 29px;
}
.buttons {
  align-content: center;
  background: rgb(77, 77, 77);
  border-radius: 0 0 5px 5px;
}
.row {
  max-width: 100%;
  margin: 3px;
}
.btn {
  border: 1px solid black;
  font-size: 20px;
  box-shadow: 1px 1px 1px rgb(44, 31, 31);
}
.btn-primary {
  line-height: 77px;
  position: relative;
  top: -94px;
  float: right;
  right: 3px;
}
.btn:hover {
  border: 1px solid black;
}
.footer {
  width: fit-content;
  margin: 0 auto;
}
.footer p {
  text-align: center;
  color: rgba(0, 0, 0, 0.75);
  line-height: 1;
}
.footer a {
  color: black;
  text-decoration: none;
}
.footer a:hover {
  text-decoration: underline;
}