* {
  box-sizing: border-box;
}

.navbar {
    width: 100%;
    background: #1abc9c;
    color: white;
    padding: 15px;
    text-align: center;
    font-size: 1.8em;
    font-weight: bold;
    position: fixed;
    top: 0;
    left: 0;
    z-index: 1000;
}

body {
    margin: 0;
    display: flex;
    padding-top: 70px;
    height: 100vh;
    justify-content: center;
    align-items: center;
    background: #2c3e50;
    font-family: Arial, Helvetica, sans-serif;
    flex-direction: column;
}

.calculator {
    margin-top: 40px;
    width: 260px;
    background: #34495e;
    padding: 15px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.4);
}

#display {
    width: 100%;
    height: 60px;
    margin-bottom: 15px;
    text-align: right;
    font-size: 2em;
    padding: 0 10px;
    border: none;
    border-radius: 5px;
    background: #000;
    display: block;
    color: #39ff14;
    font-family: 'Orbitron', monospace;
    letter-spacing: 2px;
    text-shadow: 0 0 5px #39ff14, 0 0 10px #39ff14;
    box-shadow: inset 0 2px 5px rgba(0,0,0,0.8);
}

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

.btn {
    padding: 15px;
    font-size: 1.2em;
    border: none;
    border-radius: 5px;
    background: #95a5a6;
    color: white;
    cursor: pointer;
    transition: 0.2s;
}

.btn:hover {
    background: #7f8c8d;
    transform: scale(1.05);
}

.btn:active {
    background: #16a085 !important;
    transform: scale(0.95);
}

.operator {
    background: #e67e22;
}

.equal {
    background: #27ae60;
    grid-row: span 2;
}

.zero {
    grid-column: span 2;
}

.footer {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  background: #1a252f;
  color: white;
  text-align: center;
  padding: 10px;
  font-size: 1em;
}

.footer a {
  color: white;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: color 0.3s ease;
}

.footer a:hover {
  color: #1abc9c;
}

.github-logo {
  width: 24px;
  height: 24px;
  vertical-align: middle;
}