Answers for "how to darken css color"

css darken

.button {
  color: #ff0000;
}

/* note: 100% is baseline so 85% is slightly darker, 
   20% would be significantly darker */
.button:hover {
  filter: brightness(85%);
}

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;
}