Gakken's "Mechamo Series" of kits are more complex than kits intended for younger hobbyists (though of course with adult supervision, there's no reason a bright youngster can't put them together!). This metal crab will skitter in a very -- well, crab-like! -- manner, when completed. Everything you need to build it is included in the box; requires 6 AA batteries, not included. Download the parts list and the English instructions (both are PDF files. If you don't have Adobe Reader, download it for free!)