Nice idea. I think that there are some flaws, though. For example the answer to the coin question could equally be worm, snake, fish etc. How does an echo hear? I have maps that have houses. The many teeth question could also be a cog or perhaps a bicycle. Wouldn't bannister be as good an answer to the stair question as carpet? The answer to the darkness question, it seems to me, could also be cataract, blindness, blindfold etc.