body {
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background-color: #ffffff;
  margin: auto;
  flex-direction: column;
}
main {
  min-height: 500px;
  align-content: center;
}
.calculator {
  background-color: #333;
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

#display {
  width: 91%;
  padding: 15px;
  border: none;
  border-radius: 5px;
  margin-bottom: 10px;
  text-align: right;
  font-size: 1.5em;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.btn {
  padding: 20px;
  font-size: 1.2em;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  transition: background-color 0.3s;
  background-color: #555;
  color: white;
}

.btn:hover {
  background-color: #777;
}

.equals {
  grid-column: span 4;
  background-color: #ff9500;
}

.equals:hover {
  background-color: #ffb84d;
}
footer {
  background-color: #333;
  color: white;
  padding: 20px 0;
  text-align: center;
  width: 100%;
  margin-bottom: auto;
}
header {
  background-color: #333;
  color: white;
  padding: 20px 0;
  text-align: center;
  width: 100%;
  margin-top: auto;
}
h1 {
  margin-top: 7rem;
}
.clear-btn {
  background-color: red;
}
input {
  color: #ff9500;
}