What is the currency in the Sonic universe?

I'm curious, could you elaborate on the currency system utilized within the Sonic universe? Specifically, I'm wondering what form of monetary exchange do the inhabitants of that world rely on? Is it a traditional, physical currency like dollars or euros, or does it take on a more unique, perhaps digital or in-game form? I'm eager to understand the economic landscape of this fantastical setting and how it might differ from our own.