Some of your favorite prototype sonic fun facts?
While Sonic CD had time travel, originally Sonic 2 was planned to have it first, but as a story element unlike how it's a gameplay element in CD. Here's some concept art...
(also yes yes genocidecityzone it was gonna be renamed to Cyber City Zone which was paired with Metropolis Zone which is why in the final Metropolis has 3 acts) Notice the egg thing near in the mountains in all of the pics, near Woods Zone in Now 1, Casnio Night in furture, Blue Lake Zone in ancient time. That's the original Death Egg baby! It would've still launched leaving the flooded ruins as the fifth map Past 2 with Hill Top, Blue Lake, & Tropical Summers. And despite all of this being all concept art you can still see bits of this concept still in the final game! With Emerald Hill Zone & Hill Top Zone, they're about 3 full zones apart but part of the time travel idea was to reuse level tiles.
but also the only enimes in Hill top Zone are a few types of the simple badniks, the orbinauts, aaaaand
a dinosaur! Also Hill Top having a focus on lava rising and falling and earthquakes, kinda adds to the whole past thing too!
Also Chemical Plant tiles get reused in the Death Egg Zone but i've been using Sonic Retro's screenshots and the screenshots of these two stages don't show off the similarities that well. and i hope it's alright that i didn't take these shots myself.