[SOLVED] Is reversing gravity possible in-game?

Say I want to create a puzzle where pressing a button reverses gravity.  Can this be done or will I have to set up 2 scenes (one with normal gravity, one with reversed gravity) and switch between them somehow?

In Scene >> World there are blocks: "[horizontal/vertical] gravity" and "set gravity to".
In Numbers & Text >> Math there is "negate" block.

Blocks to do this:
set gravity to (xDir: [negate[horizontal gravity]] yDir: [negate[vertical gravity]])

It will make gravity push in opposite direction.