ELLENSBURG, Wash. (AP) -- Central Washington University junior Savannah Isbey was working out in the school's Recreation Center when she first saw it: Bubble ball soccer -- full-contact indoor soccer played inside giant inflatable bubbles. "It was the most ridiculous thing I've ever seen, so it was definitely something I wanted to do," she said. Isbey was among the dozens at the Student Union and Recreation Center on Thursday who came to watch or participate in the university's latest intramural sports offering. "Basically, it's just soccer with full contact," said Jordan Stinglen, an events and intramural coordinator at the Recreation Center. Players climb inside the inflatable, tube-like balls, which are roughly 4-by-4 feet. They're held up with shoulder straps. Players inside hold on to small handles at about chest-level. Teams have four people. Most teams last week played without a goaltender. Late hits or blocks from the back are prohibited, but beyond that, it's full-contact. Beyond that, it's a free-for-all. Thursday was the second time the school has put on the game. The first was during fall quarter. When players connect, the sound fills the basketball courts with a loud, hollow "smack," closely followed by cheers from the crowd. Stinglen said rec center staff are always looking for the next thing, and discovered the game -- being played in Europe -- around the start of the school year. They looked around for where to buy the equipment, and went with Knockerball. Central, he said, is one of the first colleges in the state to get on board. The game has proven popular over the first two outings. "The first time we did it, we actually had fans all around the track, all up and down the sideline," he said. The Thursday tournament saw fewer fans than during the fall; Stinglen said a lot of students were likely at the David Garibaldi live painting event that night. Still, there seemed to be more teams. "It'll go viral, I know that," he said. Thursday's tournament was Isbey's first. At one point, she was hit so hard the ball rolled on its top, leaving her legs kicking in the air. "I'm really small, so I kind of get knocked out, but I feel like since I'm so small I can shrink into the ball," she said. It was junior Wayne Hancock's first encounter, too. "It was awesome," he said. "You can't breathe in the bubbles, but other than that, it's really cool." The balls are hot, he said. Knockerball's website says they're built with tough PVC plastic. Central's rules allow substitutions during any play stoppage, and there's a break between games to clean the tubes out. Hancock's friend's team won in the tournament last quarter and turned him on to trying, he said. "I saw a couple YouTube videos of it, and it was like, 'Oh, that's something I want to do," he said. A good hit rattles the player a bit, he said, but it's not too bad. At the first tournament there was only one major scare, Stingley said. A very small woman collided with a much larger tubed man and wasn't getting on her feet. Referees and organizers scrambled to help her, Stingley said. "She was just laughing so hard she couldn't get back up."