css variables root code example

Example 1: variables css

:root {
    --main-bg-color: brown;
  }
  
.uno {
    color: white;
    background-color: var(--main-bg-color);
    margin: 10px;
    width: 50px;
    height: 50px;
    display: inline-block;
}

Example 2: create variable in css

:root {
  --tab-count: 5;
}

#div1 {
  width: calc(100% - var(--tab-count));
}