global
<div class="enclosing">
  enclosing
  <div class="closure">
    closure
  </div>
</div>

:root {
  --globalVar: 10px;
}

.enclosing {
  --enclosingVar: 20px;
}

.enclosing .closure {
  --closureVar: 30px;

  font-size: calc(var(--closureVar) + var(--enclosingVar) + var(--globalVar)); /* 80px for now, --closureVar: 50px is used */
  
  --closureVar: 50px;
}