Speaking from an age-creator stand-point, puzzles are hard enough to design, making them to work at different levels of hardness is very hard to do in a convincing way. Different levels of hardness can only work well in action/twitch games eg. racing games or shooters. The hardness of this type of game is controlled almost solely by adjusting the AI of the opponents. Uru is primarily a puzzle game, and time and time again when it tries to be something else (wanna play Jalak...
), it fails miserably. That said, I think shooters and racing games are very fun, however, Plasma is not a good base for action games.
If an age-creator wants to give some players a break while challenging others, bonus solutions to puzzles can be added. Something like this: the easier code opens the door that continues the age's gameplay and story, while the harder to solve code opens a door to a room that contains a new piece of clothing.
Currently getting some ink on my hands over at the Guild Of Ink-Makers (PyPRP2).