how to darken backgorund color in css code example

Example: How do I make my background color darker in CSS

body {
    display: grid;
    place-items: center;
    height: 100vh;
}
div {
    width: 50vw;
    height: 50vh;
    background: linear-gradient(to bottom right, #55566a, #282834);
    border-radius: 10px;
}