* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: linear-gradient(to bottom right, #257f11, #5c3af3);
}

.calculator-container {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
}

.calculator {
  background: #1e1e1e;
  border-radius: 10px;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.5);
  width: 440px;
  padding: 10px;
}

.display-screen {
  background: #333;
  color: #fff;
  text-align: right;
  padding: 15px;
  font-size: 2rem;
  border-radius: 5px;
  margin-bottom: 10px;
  overflow-x: auto;
  white-space: nowrap;
}

#display {
  min-height: 40px;
}

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

.btn {
  background: #333;
  color: #fff;
  font-size: 1.5rem;
  padding: 15px;
  border: none;
  border-radius: 10px;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s ease-in-out;
}

.btn:hover {
  background: #555;
  transform: scale(1.05);
}

.btn.operator {
  background: #444;
}

.btn.function {
  background: #3b3b3b;
}

.btn.equal {
  background: #1e90ff;
  color: #fff;
  font-size: 1.5rem;
  grid-column: span 1;
}

.btn.equal:hover {
  background: #0078e7;
}