don't nest too deep

mq nesting

.menu-toggle { ... // ok

.menu-toggle { 
 ul {
  ... // ok
  }
}
.menu-toggle { 
 ul {
    li {
    ... // ok
    }
  }
}
.menu-toggle { 
 ul {
    li {
      a {
      ... // maybe no - your call. definitely no more though
      }
    }
  }
}