html, body {
    margin: 0;          /* Remove default margins */
    padding: 0;         /* Remove default padding */
    height: 100%;       /* Make body take full height */
    overflow: hidden;   /* Prevent scrolling */
}

.center-container-grid {
    display: flex;
    justify-content: center; /* horizontal centering */
    height: 100vh;       /* Takes up the full viewport height */
    width: 100%;
}