It was the chemical zone escalators for me. And the areas where you could fall so far without any way to rescue yourself, except to wait until you land and desperately try to climb back out.
Not for retail, but you still got it in a case that was otherwise the same as a retail clamshell. That's an additional cost that would almost certainly get cut if these consoles were coming out today.
I don't think I have the case for her 2nd in the series, but I was definitely lucky enough in 2020 to get a Genesis, Sonic 1 & 2, 3D Blast, and Spinball.