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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  color: #fff;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 0;
}

.container {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 2rem;
  margin-top: 80px;
  text-align: center;
}

.container .calculator {
  background: rgba(15, 12, 41, 0.8);
  backdrop-filter: blur(10px);
  padding: 2rem;
  border-radius: 20px;
  border: 1px solid rgba(0, 212, 255, 0.3);
  box-shadow: 0 10px 40px rgba(0, 212, 255, 0.2);
}

h1 {
  color: #00d4ff;
  margin-bottom: 0.5rem;
  font-size: 2.2rem;
  margin-top: 0;
}

p {
  color: #b0b0b0;
  margin-bottom: 2rem;
  font-size: 1rem;
}

.calculator {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  margin-top: 1rem;
}

#display {
  width: 100%;
  padding: 1rem;
  font-size: 1.5rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(0, 212, 255, 0.5);
  color: #00d4ff;
  border-radius: 10px;
  text-align: right;
  font-weight: bold;
  cursor: not-allowed;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.8rem;
}

button {
  padding: 1rem;
  font-size: 1.1rem;
  border: 1px solid rgba(0, 212, 255, 0.3);
  background: rgba(0, 212, 255, 0.1);
  color: #00d4ff;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 600;
  transition: all 0.3s;
}

button:hover {
  background: rgba(0, 212, 255, 0.3);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0, 212, 255, 0.3);
}

button:active {
  transform: translateY(0);
}

button:nth-child(16) {
  grid-column: span 2;
}

@media (max-width: 480px) {
  .container {
    padding: 1rem;
    margin-top: 70px;
  }

  h1 {
    font-size: 1.6rem;
  }

  #display {
    padding: 0.8rem;
    font-size: 1.2rem;
  }

  .buttons {
    grid-template-columns: repeat(4, 1fr);
    gap: 0.6rem;
  }

  button {
    padding: 0.8rem;
    font-size: 1rem;
  }
}