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

Walked left at the start and suddenly everything stopped functioning

Edit: hahah reaching the end and continuing to the right produces the same effect. its like the collision detaches from the sprites.

 

Heey!

 

To make Sonic roll, you don't need to run then press down, just hold down and press left or right and he'll spin.

Really buggy!

 

Here's one for you, using that ROM I linked, the bytes at offset 054B and 0550 decide the zone/act, by default they are set to 00 and 00 (Zone 0 act 0). Change them so see the other levels.

Here's a tool to help those who don't use hexadecimal editors but wish to take a look at the other acts/zones. Just drag and drop the autodemo ROM onto the application (On the file, not the console window) and then type in the Zone and Act ID's to patch onto the ROM.

 

How did you discover those thing so fast? I'm interested in what kind of debugger of SMS or Z80 you use, if any.

EDIT: It looks like those are the values for all 3 levels: (Zone 0 Act 0), (Zone 1 Act 2) and (Zone 3 Act 1) respectively.
First level:

Code (Text):

1.  
2. ROM:054A                 ld      a, 0
3. ROM:054C                 ld      (byte_D287), a
4. ROM:054F                 ld      a, 0
5. ROM:0551                 ld      (byte_D288), a
6. ROM:0554                 call    sub_734

Second level:

Code (Text):

1.  
2. ROM:05AA                 ld      a, 1
3. ROM:05AC                 ld      (byte_D287), a
4. ROM:05AF                 ld      a, 2
5. ROM:05B1                 ld      (byte_D288), a
6. ROM:05B4                 call    sub_734

Third level:

Code (Text):

1.  
2. ROM:0602                 ld      a, 3
3. ROM:0604                 ld      (byte_D287), a
4. ROM:0607                 ld      a, 1
5. ROM:0609                 ld      (byte_D288), a
6. ROM:060C                 call    sub_734

 

Holy shit

 

There seems to be more levels than just three though... A lot of them are unfinished.

 

O_O

I remember finding those unused tiles wayback when. Nice to see them arranged as intended.

 

The autodemo is so ridiculously broken, it makes Sonic Crackers look finished.

 

Wow what a mess, it's wonderful :specialed:

 

Why did they remove this?

;-;

 

!0_0!

I thought those unused tiles were for a loop.

 

Just a question guys, why do the 8 bit SMS games have enormous borders

 

It's not fair, I couldn't take a deep look at this until now, and the song has already been discovered, I feel useless

 

To edit the ROM, just use Meka. It has a realtime ROM editor

 

I disassembled the ROM myself. :v: But it looks like MJ beat me to unlocking the controls and the level/act values. xP Still going to mess around with this, and explore the levels. :v:

 

Yeah I could find the song into the ROM and I was about to port it to the final version of Sonic 2 but I guess there's no point into doing that anymore

I hate my timezone.

 

Oh do so! I mean geez, the more people having a look, the better...

I'm also pretty damn hyped with Master Emerald's findings, they seem to fill an empty picture quite well.

Combined with experience and understanding of Z80 binary instructions, and how games function on the old consoles! It seems like a drag all these years, but I'm actually rather glad in the end.

 

So I tried a bit of an experiment and tried load Zone 2 Act 3 (Sky High). It ended up loading Zone 3 Act 0, the removed act from Underground except it did not load with the mine cart...

 

Tried some random zone and act values and ended up in a horrendously broken (even more so than usual) GHZ with what looks like a massively oversized (and non-functioning) bridge.