Decked out in face paint, funny hats and neon T-shirts, tens of thousands of people emerged into a rain of glittering confetti at the 70,000-seat home of the St Louis Rams American football team.
With the tension mounting as the main event approached, music played, actors and rappers roamed the sidelines and frenzied groups waved flags and shouted chants.
But the people in this crowd, mostly in their early teens and from all over the US, hadn't come to see a sporting event. This competition, with all of its accompanying enthusiasm, was about to pit the geeks against the nerds.
The FIRST Championship is what its organisers like to call the "Super Bowl of Smarts". It's at the vanguard of a fast-expanding, privately funded movement in North American schools, meant to make academic study as exciting as athletics, with the ultimate goal of producing more American- born scientists and engineers.
Founded by Dean Kamen, inventor of the Segway electric scooter, FIRST - For Inspiration and Recognition of Science and Technology - uses sport as a model for encouraging interest in science, engineering and technology. It runs competitions for six to 18-year-olds to develop new technology and eventually build robots that compete to perform specific tasks. And there are plans to go global, including coming to the UK.
"The ultimate vision is to change our culture to celebrate science and engineering the same way we celebrate sports and entertainment," said Jon Dudas, FIRST's president and former director of the US Patent and Trademark Office.
The payoff in the US is $14 million (pound;8.8m) in university scholarships. But that's not the only thing that has helped lure 248,000 young people into the programme. FIRST makes it hip to be smart.
"There are these stereotypes that to be popular you have to be good at sports," said Thomas Fogwell, 16, whose FIRST Tech Challenge team at his high school near Philadelphia won the state championship. "But now a lot of people are looking at the robotics team and thinking that it's really cool."
Demand is high. Doctoral recipients in the sciences from US universities are increasingly non-US citizens - up from 23 per cent of the total 30 years ago to around half today. And while the population of young adults in competitor countries is growing less rapidly than in the US, the proportion studying science and engineering is rising faster.
An independent university study found that FIRST participants are more than three times as likely to major in engineering, and more than twice as likely to pursue a career in science and technology as students who do not take part.
"We need more engineers, we need more technologists, and we need more kids just to be technologically savvy," Mr Dudas said.
"There's definitely a lot of excitement," Thomas Fogwell said. "I went in and I knew absolutely nothing.
"Because it was only a small group of members, I had to learn about everything. You have all these ideas flying around the room. Everyone knows they're a geek there. You're all united in your nerdiness."