Want to try building a structure without assembling any supplies? Check out sodaplay.com's Soda Constructor. With nothing but a computer mouse, you can create a structure and test it using the gravity button and other variables. Samples on the site show moving creations to inspire visitors. They even have a Soda Race, pitting human creativity against machine learning.
So far, all I've been able to do is make a collapsing bundle of lines, but it's immensely amusing to see what happens. I imagine that someone with knack for engineering would really find this enjoyable.