@media screen and (min-width: 480px) {
  .calculator-app {
    max-width: 600px;
  }

  .buttons {
    gap: 12px;
  }
}

@media screen and (min-width: 768px) {
  .calculator-app {
    max-width: 800px;
  }

  .buttons {
    gap: 16px;
  }
}

.calculator-app {
  background-color: #505050;
  max-width: 330px;
  max-height: 400px;
  margin: 40px auto;
  border-radius: 6px;
  padding: 50px;
}

.user-input {
  background-color: #d4d4d2;
  border: none;
  width: 62%;
  font-size: 30px;
  padding: 15px 20px 20px 0;
}

.calculator-app {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 5px;
  max-width: 300px;
  margin: auto;
}

.buttons button {
  width: 100%;
  height: 60px;
  font-size: 1rem;
  margin: 0;
  padding: 10px;
  box-sizing: border-box;
  background-color: black;
  color: goldenrod;
}

.last-line {
  grid-column: span 4;
}

footer {
  text-align: center;
  font-size: 14px;
  color: #505050;
  text-decoration: overline;
  margin: 20px auto;
  border-radius: 6px;
}

a {
  text-decoration: none;
  color: goldenrod;
}