If you have boys (or girls), you probably have a bunch of hot-wheels. Instead of spending money on those play-sets, make your own with masking tape. Run it over the sofa, carpet, coffee-table and ignore all logic of physics. You can build a new track everyday, anywhere, anytime.
P.s Good to invest in those 3M stuff, rather than the cheaper options. They won’t leave sticky residue all over.
Images from: http://goo.gl/SpCr94