Corvus has a great piece over on his blog right now; he compares his experiences teaching a rescue dog how to play (which would be enough to get my interest by itself) with some guidelines on game design. Here's an extract:
Discourage Undesired Behavior Note that this rules doesn’t say punish or disallow, but discourage. Your game should not be a battlefield between designer and player. You should not take an adversarial stance with your audience. Remember that even negative attention is attention and gently discourage undesired behavior with non-threatening, non-harmful guidance. Die-and-repeat gameplay only appeals to a small segment of the game playing public, so give the rest of your audience plenty of gentle discouragement when they wander astray.
Prod Corvus for pictures of Eliot!