/* Reset and base styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', sans-serif;
}

body {
  background-color: #121212;
  color: #ffffff;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding-top: 60px; /* space for navbar */
  min-height: 100vh;
}

/* Navbar styles */
.navbar {
  position: fixed;
  top: 0;
  width: 100%;
  background-color: #1e1e1e;
  padding: 12px 24px;
  box-shadow: 0 0 10px rgba(0, 255, 255, 0.1);
  display: flex;
  justify-content: center;
  z-index: 1000;
}

.navbar ul {
  list-style: none;
  display: flex;
  gap: 24px;
}

.navbar li a {
  color: #00ffcc;
  text-decoration: none;
  font-weight: bold;
  transition: color 0.2s ease, text-shadow 0.2s ease;
}

.navbar li a:hover {
  color: #ffffff;
  text-shadow: 0 0 8px #00ffcc;
}

/* Calculator container */
.calculator {
  background-color: #1e1e1e;
  border-radius: 12px;
  box-shadow: 0 0 20px rgba(0, 255, 255, 0.2);
  padding: 20px;
  width: 320px;
  margin-top: 20px;
}

/* Display screen */
.display {
  background-color: #2a2a2a;
  color: #00ffcc;
  font-size: 2rem;
  padding: 15px;
  border-radius: 8px;
  margin-bottom: 20px;
  text-align: right;
  overflow-x: auto;
}

/* Button grid */
.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

/* Individual buttons */
button {
  background-color: #333;
  color: #fff;
  font-size: 1.2rem;
  padding: 15px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background-color 0.2s ease, transform 0.1s ease;
}

button:hover {
  background-color: #444;
}

button:active {
  background-color: #00ffcc;
  color: #000;
  transform: scale(0.98);
}