The instructions say to use LEGOs to "build a chassis of your design that supports four wheels 2 inches or larger in diameter." It then says to glue the LEGOs together "for extra durability"... but we all know that's not the way to go (at least not if you're a purist)! The rest of the instructions tell how to set up the solar panel. Apparently, in direct sunlight, the bot should "scoot along at 2 feet per minute," which isn't fast by any standards but should provide a sense of satisfaction that you managed to build a working solar rover out of LEGOs!
It was good to see this article in PopSci, as I suppose it helps to promote LEGOs and the things that can be done with them. I probably won't be trying this myself, but I'd be interested to see what people think of this design in the comments.