Here's a very quick update showing the in-game options for the sandbox mode!

When in sandbox mode, you can open this menu any time during the game and change the values, on the fly.
This works on a per-player basis, so when playing in split-screen, each player can mess with these sliders, independently!
I'm glad I got this style of options menu (that is independent of the pause screen) to work—I want to re-use this style of UI for "photo mode" to give a bunch of camera options (i.e. focus, field of view, and maybe even filters?)