The "Flash Belt" was not a single game, but a series of interactive projects uploaded between 2004 and 2010, most notably by a user named (a pseudonym referencing both a Kamen Rider vehicle and a classic Newgrounds troll). The concept was brilliantly simple yet technologically ambitious for Flash:

The Digital Henshin: How the "Kamen Rider Flash Belt" Became Newgrounds’ Most Unlikely Cult Classic

To understand the Flash Belt, one must first understand the context. In the mid-2000s, Newgrounds was a creative powder keg. Amateur animators and game developers, armed with Macromedia Flash, were reimagining their childhood obsessions. For Western fans of Kamen Rider , access to the show was difficult—only a handful of series like Kamen Rider: Dragon Knight had been localized. This scarcity bred creativity. Fans didn’t just want to watch the transformation; they wanted to simulate it.