body {
  font-family: 'Arial', sans-serif;
  background: linear-gradient(45deg, #ff9a9e, #fad0c4);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  flex-direction: column;
}

.container {
  text-align: center;
  padding: 10px;
}

.heading {
  font-size: 2.5rem;
  color: #fff;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.4);
  margin-bottom: 20px;
}

.calculator {
  width: 350px;
  background: #fff;
  border-radius: 15px;
  box-shadow: 0px 8px 20px rgba(0, 0, 0, 0.2);
  overflow: hidden;
}

.display {
  background: #f3f4f6;
  padding: 20px;
  border-bottom: 2px solid #ddd;
  min-height: 100px;
}

#input-display {
  font-size: 1.8rem;
  color: #333;
  text-align: right;
}

#result-display {
  font-size: 1.5rem;
  color: #666;
  text-align: right;
  margin-top: 5px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  padding: 20px;
  background: #f8f9fa;
}

.btn {
  padding: 20px;
  font-size: 1.5rem;
  border: none;
  border-radius: 10px;
  background: #e3f2fd;
  color: #333;
  cursor: pointer;
  transition: all 0.2s ease-in-out;
}

.btn:hover {
  background: #bbdefb;
}

.operator {
  background: #fbe9e7;
}

.operator:hover {
  background: #ffccbc;
}

.equal {
  grid-column: span 2;
  background: #c8e6c9;
}

.equal:hover {
  background: #a5d6a7;
}

.clear {
  background: #ffcdd2;
}

.clear:hover {
  background: #ef9a9a;
}

.backspace {
  background: #ffe0b2;
}

.backspace:hover {
  background: #ffcc80;
}

.refresh {
  background: #d1c4e9;
}

.refresh:hover {
  background: #b39ddb;
}

/* Responsive Styles */
@media (max-width: 480px) {
  .calculator {
    width: 100%;
    max-width: 300px;
  }

  .heading {
    font-size: 2rem;
  }

  .btn {
    padding: 15px;
    font-size: 1.2rem;
  }

  #input-display {
    font-size: 1.5rem;
  }

  #result-display {
    font-size: 1.2rem;
  }
}