There are plenty of fun retro gaming inspired Lego sets on the market today. Both the Lego Icons Atari set and the Lego Super Mario Game Boy , for example, are pure nostalgia. Yet as cool as they are, therere definitely lacking a little something: I wish they were playable and had actual, working game systems inside. Of course, this would make them quite a bit more expensive and probably more complicated to build, but it would also be an incredible upgrade. If building your very own working...