Three emotions dwell in the heart of every geek: an innate desire to build things, a fondness for interlocking plastic blocks, and the impulse to destroy the earth with killer robots. One product satisfies these urges - Lego's RoboLab, available from educational distributors such as Pitsco Lego Dacta ( www.pitsco-legodacta.com ). Based around a $125 computerized central control, your Mac, and the unblinking infrared eye that allows the two to communicate, RoboLab kits combine motors, sensors, and enough Lego bricks to kick-start a reign of robotic terror. The kits, which sell for $110 and up, are designed for students, but why should they have all the fun? Especially when there's an entire world to enslave with plastic kill-bots.