:root{
    --var-10: 10px;
    --var-15: 15px;
    --var-20: 20px;
    --var-25: 25px;
    --var-30: 30px;
}

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

html, body{
    width: 100%;
    height: 100%;
}

a{
    text-decoration: none;
}