I’ve just completed a prototype of a digital version of Legos. There were a series of interesting design challenges associated with making the transition from physical toy to computer game, but the end result seemed to turn out ok.
You can grab the game here. Left click to drag the bricks, and right click to detach them. Escape will clear them and end the program.
Of course the game could use a bit of polish, but I think it demonstrates the concept. If you are really interested in the design choices behind the demo, you can grab the writeup in pdf form here.