xxxxxxxxxx
.button {
color: #ff0000;
}
/* note: 100% is baseline so 85% is slightly darker,
20% would be significantly darker */
.button:hover {
filter: brightness(85%);
}
xxxxxxxxxx
filter: brightness(85%);
> 100% = baseline
> 85% = slightly darker
> 29% = significantly darker
xxxxxxxxxx
body {
background: url("/backgrounds/city.jpg") center/cover no-repeat;
background: linear-gradient(rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5)), url("/backgrounds/city.jpg") center/cover no-repeat;
}