/* General page setup */
body {
  display: flex;
  flex-direction: column;       /* stack title, calculator, footer vertically */
  justify-content: center;      /* center vertically */
  align-items: center;          /* center horizontally */
  height: 100vh;
  margin: 0;
  font-family: Arial, sans-serif;
  background: linear-gradient(135deg, #74ebd5, #ACB6E5);
}

/* Title at the top */
.title {
  text-align: center;
  margin-bottom: 20px;
  font-size: 2em;
  color: #222;
  text-shadow: 1px 1px 2px rgba(0,0,0,0.2);
}

/* Calculator box */
.calculator {
  background: rgba(34, 34, 34, 0.95);
  padding: 20px;
  border-radius: 15px;
  box-shadow: 0 5px 20px rgba(0,0,0,0.3);
  display: flex;
  flex-direction: column;
  align-items: center;
}

/* Display screen */
#display {
  width: 100%;
  height: 50px;
  margin-bottom: 15px;
  text-align: right;
  font-size: 1.5em;
  padding: 5px 10px;
  border: none;
  border-radius: 8px;
  background: #eee;
  color: #222;
}

/* Buttons grid */
.buttons {
  display: grid;
  grid-template-columns: repeat(4, 60px);
  gap: 10px;
}

button {
  height: 60px;
  font-size: 1.2em;
  border: none;
  border-radius: 10px;
  background: #444;
  color: white;
  cursor: pointer;
  transition: transform 0.1s, background 0.2s;
}

button:hover {
  background: #666;
  transform: scale(1.05);
}

button:active {
  background: #888;
  transform: scale(0.95);
}

/