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

$globalVar: 10px; // global variable
.enclosing {
  $enclosingVar: 20px; // local variable
  .closure {
    $closureVar: 30px; // local variable
    font-size: $closureVar +$enclosingVar+ $globalVar; // 60px, $closureVar: 30px is used
    $closureVar: 50px; // local variable
  }
}