Cursor 10

[Sol]

uh
that's how you beat the game
you sacrifice a cursor to hold that switch

then you use 3 more on the 15th floor to hold the three switches
your last cursor (or at least the one you beat the game with) should be the one right after the third switch unless you're going for points

you have to hold all 4 switches to open the stairs to the roof

It's not the one that reveals the stairs though, it's before that one I think. I know you need a cursor for that switch and three more for the later three switches. Like I said, I beat the game.