Lineart graphics, Shooting gallery, and disintegrating ladders?

I've been trying unsuccessfully to remember the name of a game I played back in my youth. It was a graphical adventure, (graphics were on the order of MSPaint art, though.) It ran in a window on Workbench, might have been point-and-click, but I can't rightly remember, since I was roughly 7 at the time (it's definitely pre-1989, since our Amiga was stolen then.)

Anyway, there's only two major elements that I can remember, one being a shooting range (which it's not a good idea to cross), and a set of three different-colored ladders leading up to a ledge, which disintegrate when I try to climb them (from my first-person perspective.)

Any ideas? I'd really like to find this game, and just maybe my 26 year-old brain can*finally*finish what my 7-year-old brain couldn't.