Lego isn't for precious types. Part of the fun is sitting back and admiring your creation for a few minutes before smashing it up and starting over. You can do this with the same disregard for your achievements as Lucas paid his own masterful trilogy, before vandalising it in his 'special editions'.
So you can't die (you're just infinitely rebuilt when you lose a life), and you can't even fail as such, but you'll still keep playing. Happily, it looks great on the DS, with smoothly rendered characters and backdrops.
There are problems though, mainly relating to the camera and twitchy digital controls that can make seemingly simple tasks extremely frustrating. It's also a shame that scarcely any use is made of the DS' features - just a permanent menu clogs up the touch screen. Still better than the GBA version, though.