The game arrived really fast and WOW, it looks like it's an official sega release. The box is sturdy and looks great on my shelf and the game itself is super fun. I love being able to spindash and use homing attacks in Sonic 1, it's kind of OP and I love it. I also love seeing Shadow get his own "classic era" design and animations. He's not just a reskin of Sonic, he actually skates around which is super cool to see.
As a Shadow fan, I'd of course want to see you guys somehow include chaos powers in other hacks like this one. And if I had to conjure a complaint/request is that I hoped the music would be a little different. It feels kind of goofy to have the plucky Sonic 1 music in the background while playing as Shadow. I know the Genesis sound bit can't do the rock and roll that he's known for but some more stylized music would be another really neat change I think. But that's just a nitpick. The game plays amazingly and I love it a lot. Definitely gonna go in for the other hacked carts you guys sell.
