Sega Swirl is a puzzle video game released in 1999 for Windows, in 2000 for Sega Dreamcast, and in 2001 for PalmOS (according to Moby Games); an Adobe Shockwave version was available back when you could play Shockwave games on the web.
On the Windows version, the appropriately swirly (and curly) Curlz is used for menus, and in-game text; advertising for all versions often uses Curlz. Curlz was made available only a few years earlier, in 1995.
The PalmOS version does not use Curlz, nor any other custom font. Probably a deliberate choice in order to fit the game onto some quite limited PalmOS models.
The game was released as both a teaser and a demonstration of the Dreamcast’s online play; the Windows version was freely downloadable, and the Dreamcast version appeared as a cover-disc and in various promo discs. The Dreamcast had a built-in modem and Sega Swirlz supported online competitive play, including with players of the PC version.