"At the end of six weeks we have to bag it up, tape it closed and leave it alone" until the competition, Koenig said. "They check your seal." At the contest, "you get one day to work on it. ... This is so everyone gets the exact same amount of time."

Teams around the world follow the same guidelines: a robot can weigh up to 120 pounds (54 kg), not including the battery and bumpers (padded "fenders" around the base and above the wheels).

The Bits and Bots team used four bathroom scales to keep within their limit; they had to take off a supporting bar to reach the weight limit, Leslie said.

BRAINS AND CREATIVITY

"What set us apart is a catapult design," said R.A. Long sophomore Alex Boyd, one of the drivers and the lead programmer for the bot.

In the Oregon regionals in Portland, Bits and Bots were the only team with a catapult, and they came in third in that state contest. In Seattle, two other teams had the catapult design.

Before they settled on the catapult, they tried five prototypes, Koenig said — pneumatic types, a kicker that operated like a leg, and two spring mechanism, one of which pulled the ball down and then hit it as it came back up.