:root {
    --card-back-color: #991b1b;
    --card-back-image: repeating-linear-gradient(
        45deg,
        transparent,
        transparent 8px,
        rgba(255, 255, 255, 0.25) 8px,
        rgba(255, 255, 255, 0.25) 12px
    );
}

.card-back {
    background-color: var(--card-back-color);
    background-image: var(--card-back-image);
    background-position: center;
    background-repeat: no-repeat;
    background-size: 100% 100%;
}