Adventurers plops, ripe for the grabbing

The Warm Village is nestled tight in the bottom of a mountain valley. The peaks are too high to traverse. The only way in or out is The Tunnel. One early spring as the snow & ice is being cleared out of the entrance to The Tunnel, the workers find it inhabited by ferocious Yetis. Some workers are eaten. One small timid worker finds himself cut off from everyone else & must find his way back. He notices that the normally straight tunnel has been transformed into a mystical labyrinth. Each puzzle along the way requires him to draw a picture (submitted by the readers) to solve it & move on. Once he arrives back in The Warm Village, he recruits some of the townsfolk to help him, each with their own drawing style, & together they work to clear out the rest of The Tunnel to reconnect the road to The Outside World.