We first saw at glimpse of it at the end of the first reveal trailer during E3, thinking it was probably just a nod to represent Mario/Sonic's root but it seems Sega is doing the whole thing with multiple events to be playable in a pleasant 8-bit aesthetic reminescent of Tokyo 1964.
Also, like you can hear during in some parts, there's an actual announcer while playing !
Probable that we haven't seen everything yet (Story/Adventure mode ?) and we'll get more info during the next Direct !
Here's the showcase at Gamescon :
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