#loader {
    background: #ccc;
    opacity: .5;
    position: fixed;
    width: 100vw;
    height: 100vh;
    z-index: 9999;
    top: 0;
    left: 0;
    display: flex;
    justify-content: center;
    align-items: center;
}

#spinner {
    border: 16px solid #f3f3f3;
    border-top: 16px solid black;
    border-radius: 50%;
    width: 120px;
    height: 120px;
    animation: spin 2s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}