Time for a browser game; this one's right down the line between "games as art" and "games as brutal platforming challenges".
Terry Cavenagh's Don't Look Back is a reimagining of the Orpheus myth via the medium of the browser game; as the player, you'll descend into hell (this time with a handgun), and retrieve your beloved. The catch: once you've found her, you have to return to the surface without ever looking back.
This is not an easy game but it's not unfairly hard. Each individual room is very tricky, but you've got unlimited lives and a checkpoint at the start of each room, so you'll never have to replay an easy bit to get another crack at the hard bit. If more platformers were like this I'd be inclined to spend more time with the genre.
Don't Look Back is thoroughly entertaining, and an early contender for many of next year's indie and casual awards, so go check it out now before you're the only kid who hasn't.