* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}

body {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: linear-gradient(135deg, #0f0c29, #302b63, #24243e);
  color: #fff;
}

.calculator {
  background: rgba(255, 255, 255, 0.08);
  backdrop-filter: blur(12px);
  border: 2px solid rgba(255, 255, 255, 0.15);
  border-radius: 20px;
  padding: 20px;
  width: 280px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.5);
  animation: fadeIn 0.6s ease-in-out;
}

.title {
  text-align: center;
  font-size: 22px;
  margin-bottom: 15px;
  color: #ffda79;
  text-shadow: 0 0 10px #ffda79;
}

.display {
  background: rgba(0, 0, 0, 0.7);
  border: 2px solid #6c63ff;
  border-radius: 12px;
  padding: 15px;
  font-size: 28px;
  text-align: right;
  margin-bottom: 15px;
  overflow-x: auto;
  color: #00ffab;
  font-family: "Courier New", monospace;
  box-shadow: inset 0 0 12px rgba(108, 99, 255, 0.6);
}

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

.btn {
  padding: 15px;
  font-size: 18px;
  border: none;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.12);
  color: white;
  cursor: pointer;
  transition: 0.2s;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.btn:hover {
  transform: scale(1.1);
  background: #6c63ff;
  box-shadow: 0 0 15px #6c63ff, 0 0 25px #6c63ff;
}

.equals {
  grid-row: span 2;
  background: #00ffab;
  color: black;
  font-weight: bold;
  font-size: 22px;
}

.equals:hover {
  background: #00e69d;
  box-shadow: 0 0 20px #00ffab;
}

.operator {
  color: #ff4b5c;
  font-weight: bold;
}

#clear_btn {
  color: #ff4b5c;
}

#x-btn {
  color: #ffda79;
}

@keyframes fadeIn {
  from { opacity: 0; transform: scale(0.9); }
  to { opacity: 1; transform: scale(1); }
}