body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: linear-gradient(135deg, #3a3d40, #181818);
    font-family: 'Poppins', sans-serif;
    color: white;
    background: url(shazaib.jpg);
    background-size: cover;
}

.calculator {
    background: #222;
    padding: 20px;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    width: 320px;
}

.display {
    width: 100%;
    height: 60px;
    margin-bottom: 20px;
    text-align: right;
    padding: 10px;
    font-size: 32px;
    border: none;
    border-radius: 10px;
    background: #333;
    color: #0f0;
    box-shadow: inset 0 4px 8px rgba(0, 0, 0, 0.4);
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
}

button {
    padding: 20px;
    font-size: 20px;
    border: none;
    border-radius: 10px;
    background: #444;
    color: #fff;
    box-shadow: 0 4px 10px rgba(0,0,0,0.3);
    cursor: pointer;
    transition: all 0.3s ease;
}

button:hover {
    background: #555;
}

button:active {
    box-shadow: inset 0 4px 10px rgba(0,0,0,0.5);
}

button:nth-child(4n) {
    background: #f39c12;
    color: white;
}

button:last-child {
    background: #27ae60;
    color: white;
}

button.equalBtn {
    background: #e74c3c;
    color: white;
}