SO the lift opens automatically on top floor and ground floor. To close it and get it moving, you have to be inside the lift. No tricks.

So, Mr. Javier, you just ruined a puzzle. This wasn't a hard puzzle, just a simple trick.Most people answer it by sending Ambroisa (the lightest) down every single time. Nobody even got a chance to do that and you solved the puzzle.

Next time, maybe a little harder puzzle for you MR.