My theory is that there are 2 different signs and the similarities could just be because they are reusing the same chunk. For example maybe the first sign is shown then it goes into the red text running section then it ends with Sonic passing the second sign then running off-screen/fade out
Looking at it closely, I think you're right - the background seems to suggest that there are indeed two instances of the sign. That certainly explains why the mountains looked so different in two shots we'd originally thought were very close together! However, if that's the case then there's at least one area of the demo we currently have no screens of - given that the ground in the starting area is pretty near the bottom of the screen, Sonic must logically climb a small hill at some point after running underneath the first enemy, in order to be able to descend one again when encountering the first sign.
Two identical signs are located in the exact same spot at the bottom of two identical small hills? It's a neat idea, but I don't quite buy it. How many planes are supposed to be scrolling at one time in this demo? Like seven or eight? Surely that would mess with object positioning in the background/foreground? If I'm not understanding something, please enlighten me!
Or the level loops horizontally, and the background gets out of sync. Interestingly we have seen this sort of thing before in the fan community: this Amiga demo can'd do parallax but it's a similar idea - Sonic automatically moving to the right.
Remember, if it's anything like the final then the stages will be made up of pre-made 256x256 chunks. That means the hill, sign etc. are likely all one chunk of terrain - if that's the case, reusing the identical chunk at two points in the layout would actually make more sense than having to make a whole separate chunk where the sign was on flat ground or something. I'm not 100% convinced we've got it right, but the anomaly with the background is interesting and there being two signs does seem to be a possible explanation. That's another possible cause, and the area with the red text at the end does look like it wouldn't have trouble looping straight back to the start if needed. However, there's two points which are currently stopped me from believing that this is the case in this demo: Firstly, at the start of the stage Sonic is stood off to the left of the screen (best seen in the old blurry EGM shot, which appears to show the full width of the screen) - this suggests a fixed camera boundary at the start of the stage, as if it looped you'd expect him to start off centered so that it wouldn't look different on subsequent loops. Secondly, there's only one shot where the background doesn't match up with what we'd otherwise expect. Everything else in the entire run-through seems to match up fine with surrounding shots, even though they all originate from multiple disparate sources. For these reasons, I'm inclined to believe that the demo only ever displayed a single run-through of the stage before returning to the SEGA logo or title screen, similar to how the attract mode demos work in the final game.
I would have thought that, but given we've seen screenshots from multiple sources now, and they're all very similar, I suspect the "level" isn't very long (as in, maybe not much more than "up the hill, down the hill"). If this is a rolling demo, you're probably going to want to prioritise "gameplay" over title screens and logos, and you'd also want to have Sonic moving to show off all the parallax layers, so I would imagine there's more than one "loop". That being said it would be fun if this iteration of "Green Hill Zone" literally just had one green hill in it. And it turns out the name has been an inside joke for 30+ years. (Honestly I wouldn't put it past them in this first game. Marble Zone because it has "marble" in it. Sparkling because it "sparkles". Labyrinth because... well.)
Hmm... That unused level layout has always mystified me. TCRF lists a diagram of the unused level while also noting how any non-solid chunk was overwritten. However, what few people have considered is making diagrams of the other levels in the game and comparing their layout. If a level has a similar chunk layout to the unused level (funky numbers aside), we might be able to deduce if this unused level is a earlier iteration of another level judging by the 00s and 01s.
