Believe it or not, there is more than just Sonic content at SAGE. Other gaming IPs are featured there, as well as more original creations. For example, Super Mario Flashback is at this year's SAGE. It's "a fanmade love letter to the Mario franchise that brings back stages from his former 2D and 3D adventures". The demo has 7 Power Stars and 3 Green Stars that players can collect, along with "something special" you can get for collecting all of the latter.
So, go and download it! You can do so here.