Heavyweight Thunder is a boxing game that features a combination of first- and third-person fights against fictional contenders from around the globe.

The game sports a proprietary SimuPunch system that turns mouse movements into body blows, uppercuts, and combos. Players fight in a number of settings, from bars to blockbuster arenas, and they can use their newfound wealth to buy cars, clothes, mansions, and to take groupies out for a night on the town. Fighters can also blow their earnings in the game's casino, where they can gamble on blackjack, poker, slots, or boxing matches.

Heavyweight Thunder also offers a role-playing element. As players rise to the top, they help manage the careers of up-and-coming fighters. They can also use the game's tools to design boxers and leagues or create tournaments and exhibitions that can be shared via the Web.