It's kinda like the older game Spear-toss.
You see how far you can launch Santa from the catapult using your mouse.
To start the catapult rolling, click on the gamescreen, let go, then when you've judged it's close enough to the crevasse, click and hold your left mouse button to cock it, then let go and shoot Santa across.
Be sure to let Santa go over the edge at least once to hear the old Goofy scream.
(and yes, this means I finally have working speakers again, fly.)
http://www.joker-inc.com/.joker?link=slingshotsanta.swf