(GG) Sonic 2 Auto Demo Prototype (1991-12-05) - Info & Download

That boss only causes trouble on the Game Gear - the difficulty curve almost makes sense on the Master System, so it's understandable in that context at least why Underground comes before Sky High.

Why they moved Green Hills further in is anyone's guess. My theory is so people wouldn't mistake Sonic 2 for Sonic 1, which would otherwise have very similar opening levels. That or Underground Zone was too short for a mid-game level.

 

Although these preliminary designs are impressive, we have to realise that they were far too ambitious. Remember they went from this buggy mess to a finished game in less than 9 months.

 

Also original level order reflects the first game maybe?

1. Green Hill
2. Bridge
3. Jungle
4. Labyrinth
5. Scrap brain
6. Sky base

vs.

1. Green Hill
2. Sky high
3. ???
4. Underground zone
5. Gimmick Mt zone

Unaccounted:
6. Aqua Lake zone
7. Scrambled egg
8. Crystal egg

 

The Green Hills boss, and the whole of act 3 is much harder than the underground boss on the master system, due to the amount of unfair blind jumps you have to make and hitting springs. I'm guessing Underground was the easiest level so they were switched.

 

Green Hills Act 3 might be the reason for the shift, unless you know about extending your jump distance with the ground roll jump technique you're pretty much fucked. As a kid act 3 was always the level that stopped me progressing further until I learned that move. I do actually wonder if the technique was intentional, I mean where the hill goes down on to the springs the level design is pretty much encouraging you to do it. If so it's shame it wasn't conveyed better, it's the equivalent of the barrel only more useful.

 

Just noticed the palmtrees at the end of GHZ Act 3, whilst present in the autodemo, are shorter in the mockup screen. There's also less detail in the magazine pic.

I always reckoned the difficulty of Act 3 was the reason GHZ was pushed back further in the game.

 

There are two kinds of palmtrees. The big and the small ones. The mockup scene isn't present in the demo at all.

 

For the record (although you could probably guess this), the graphics of this AutoDemo match the final game's ending (at least for the ground and... "bushes" - the trees and clouds were swapped).

 

I have a theory, When they changed they levels around, presumably the random bounces were switched off in the master system build to make the first level easier, but they forgot to do it to the GG one (last minute change?). It's something we should ask glitch about, as he has picked the game apart, and could tell us if there's any code bypassed to indicate the bounce heights were switched off for the master system version, rather than added to the game gear one.

 

I made great progress with the disassembly today. The level art, mappings and layouts have been split out. They obviously hadn't written the level compression routines yet since they're stored uncompressed in the ROM. Aspect Edit can't load uncompressed level layouts so you'll need to compress them first (use the s2pack utility from the Sonic 2 disassembly - included in the repo).

I didn't see maps for the Underground zone acts so here they are:
UGZ1
UGZ2

Wrt the UGZ boss, the speed of the bouncing balls depends on the number of seconds on the timer at the frame the object is spawned. The speed value is set to 256 + seconds (where seconds is a BCD encoded byte). That's taken from the SMS disassembly. I haven't explicitly looked at a GG ROM but I'd expect them to be the same.

 

Holy balls. Underground looks incredible.

It's funny how the physics and collision make the layout suck.

(Of course they seem to have made the rails quite recently as it appears to have overwritten some block tile used on the rest of the layout.

 

And here are the maps for the last two stages (well, the ones with tilesets):
Sky High 1
Sky High 2

Sky High 1 is a very rough sketch of the act, while whatever Sky High 2 was going to be was seemingly chucked out for the final game's rainy hang glider level.

 

Those Underground Zone maps are quite spectacular. Is there some technical reason why the final game couldn't have any of the "rocky" sections because it feels like a big step back.

 

This may sound silly but playing the game on kega Fusion emulator - How do you get past the first level as their isn't actually an end to the level?

 

You can't.

You either need an Hex editor or MEKA emulator.

Hex edit the rom at offset 0x054B and 0x0550

First value controls zone and second controls act.

Edit:

I received a PM on SMSPower

I don't know the validity of this suggestion, though. I'm just doing the guy a favor ;p

 

You absolutely can in Fusion, just enter these codes under Game Genie/PAR:

00054B:XX
000550:XX

Replace the XXs with a value - first code controls zone (00-03 valid), second controls act (00-02 valid).

 

Oh I never knew how these worked, so game genie codes are just addresses and the byte the change? LOL

 

Excellent!

Thank you sir

 

Game Genie codes were usually obfuscated in some form, but Action Replay codes were naked addresses and values. That's how I started hex editing way before I ever owned a PC. :D