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Sonic the Hedgehog 2 Beta
Hacking Guide

Esrael L. G. Neto (esrael@emulationzone.org)
And
James R. Grant (nayr@emulationzone.org)

* Recent updates

Using a hexadecimal editor is possible to modify the game, editing it byte to byte. Knowing where it is each instruction and altering it correctly you can personalize the game. You can draw other character in the place of Sonic but this is not easy since he has that if fact point to point. To alter the name of the levels in the selection menu and in I title it of the levels. But to program the game it is necessary that he is in the binary format, it is not very difficult to convert the game for binary, you can use a conversion program or the emulator Genecyst that has the option DUMP ROM, that makes the conversion.

LEVEL SELECT MENU

The Level Select Menu of Sonic 2 Beta uses a format of plane text of 26 characterses for line. all the lines can be typed texts of up to 26 characterses besides the lines that show only STAGE 1 and 2. The first space begins in the letter G of the word GREEN HILL and the last space finishes in I number it 0 of STAGE 0, the first space begins where it finishes the space of the first line and like this until the end of the screen of selection of levels. see the list of the levels and the respective addresses below in the editor hexadecimal. Obs: In the editor you will see addresses for example in hexadecimal in the following format 000035B9. But in the page you will see that same address represented by 3B59. Observe the illustration of the editor hexadecimal and soon I lower the relationship of all the levels and its respective addresses..

The name of the levels uses a group of characterses Non-ASCII. It is necessary to know the equivalence of the letters to modify the name. Observe the table below and modify the names. Run the game and go to the menu of selection of levels and see the names that you placed.

 You can also define the level that the game loads when pressing " START " in the menu of selection of levels. The place where the game search the levels when pressing " START " in any level in the menu of selection of levels are starting from the address 3AD4 it Observes the image of the editor hexadecimal. 

The cursor in the image is exactly in the address 3AD4h, this is the initial address for load of the levels of the menu of selection of levels. The menu of selection of levels uses 2 bytes to select a level. the 1st. byte defines the zone to be loaded the 2nd. byte defines the act to be loaded, in the byte that configures the act the 00 it indicates act 1 and the 01 it indicates the act 2, the only exception it is the level Metropolis Zone Act 3 that it is represented by 05-00, the others they follow the rule above. To facilitate the understanding and the edition of the levels I created two tables one with ID of the levels that will be used in the 1st byte of the levels. Observe:

Notice that some numbers are jumped as of the 01, 03, 06 and 09. In spite of not existing a level name for these ID's in the relationship and nor in the menu of selection of levels. If you place these ID's that you are being missing you he can acquire the lost levels (he Makes the experience and see the results). it Observes the table with the standard of the levels location and soon after an explanation.

The table above indicates where they are located the configuration bytes in the menu of selection of levels. The 1st. I address of the table it indicates the byte of the zone and the 2nd. address indicates the act byte. Example in the address 3AE6 you will see the byte 08 (Hidden Palace zone) and in the address 3AE7 you will see the byte 00 (Act 1). In case you want to turn an inaccessible level in the menu of level selection he types 80 in the byte of the zone. 

MUSIC LEVEL

You can also choose the music to be played in the levels. The format is of just a byte for level and it is very simple. To place another music of its preference, play the sounds in the sound test, write down the number of the music and place in the byte that represents the chosen level. Obs: for technical questions the level Death Egg cannot have its selected music. See below in the table the location of the selection of music. Also observe that for the correct operation will be necessary to alter the bytes in the two addresses listed .  below.

START LEVEL

You can define which level the game loads when pressing " START " during the screen title, that now is NEO GREEN HILL. For so much it goes to the address 383A and 383B, you will see the bytes 0F-00 that belong NEO GREEN HILL act 1, Change these bytes using ID of the levels in the selection menu and select the level that the game should load when pressing " START ". Former: if you change these bytes for 07-01 the game it will load the level HILL TOP act 2 when pressing " START " in the screen title.

ORDER OF THE LEVELS

Now the sequence of the levels of the game is NGHZ 1-2, CPZ 1-2, HTZ 1-2, GHZ 1-2, but it is possible to alter the order with that the levels are exhibited in the game. The sequence begins in Offset BF9A á BFDD. The format is similar to the menu of selection of levels, that is to say two bytes for level. The picture below exhibition the current sequence of the levels in order in that are played. Change ID to go for a level different from the specified.

TITLE CARDS

Originally these are disabled in the version beta, but you cannot you activate them. Click here to get IPS  and also an explanation for the case of you to want to change the name of the levels.

CHANGING OBJETOS

You can also alter objects in the levels as badnicks, lives, obstacles, etc... The configuration of the objects in the levels uses 6 long bytes, being in the format XX-XX-YY-YY-OO-VV. Explaining to X's better indicates the horizontal position in the screen, Y's indicates the vertical position in the screen, O's indicates the objects they be she placed and V's indicates the possible variations of each object. To obtain the exact location of the place where you want for the objects, make the code of the debug mode and write down the first line of coordinates in the place of SCORE, These will be the coordinates that you should type to place the object in the wanted place. See the location where the game search the objects of the phases. The levels finish the mapeamento before the bytes FF-FF-00-00-00-00. Starting from these bytes next level begins. 

  Selects a level to exhibit the available objects and its coordinates.

I BEGIN OF SONIC IN THE LEVELS

In this part you can define in that point of the screen Sonic begins. To select a place different from the original. Use the way debug. Go to the place from where you want to begin and write down the coordinates (first line in the place of Score), Tends in hands the coordinates it places them accordingly in the place of the chosen level in the address of the table below.

DEBUG

In this part you can define which the objects will be loaded during the way debug. See as configuring the debug. (If you go a researcher of Roms, he/she will see objects that are disabled in the way debug). THE Format to configure the objects in the way debug is OO-PPPPPP-VV-SSSSSS where: OO is the object, PPPPPP it is the point of assembly of the object (it Consults the properties of the OBJECTS to catch this information), VV is the variant of the object and SSSSSS it is the address of the sprite regarding the object in V-RAM (necessary Sprite has to be loaded in V-RAM). To have success in the configuration he chooses an existent object in the level (You can use of another level, but he had needed to do special configurations). For you to understand the format I will get an object of GREEN HILL, that is to say the monitor. former: 26-00B6D2-07-00-0680. Separating the bytes has: 26 monitors, 00B6D2 Point of Assembly of the monitors, 07 monitor of invincibility, 00 frame set  and 0680 search of Sprite in VRAM. Now see below in the table the location of the levels for DEBUG.

(*) All these levels can have more objects, because they have objects for the debug that are disabled. If you move in the pointers it can activate these objects. Activating these objects you will have the ALLIGATOR, the RHINOCEROS and a PIRANHA in GREEN HILL and in HIDDEN PALACE, even so without SPRITES because they are not usually loaded in V-RAM.

LIVES

In this part you can define with how many lives the game it begins. You can select up to 255 lives, even so above 99 the counter won't show the real number. The table below exhibition the values pattern of the Game. For example if you want to begin with 10 lives he/she should type the value in hexadecimal that is to say 0A. 

RINGS

In this part you can select the value of each ring. You to choose that each ring to the ditch from 0 to 8 to be collected. If you want a difficult game he/she makes each ring to be worth 0. he/she Sees the table I lower a relationship of the possible values for the rings.

LOST OBJECTS

0xAEB6 - Big Ring (Sonic 1) (part 1)
0xAF80 - Big Ring (Sonic 1) (part 2)
0xC068 - Special Stage - Title Cards
0x13F00-Springs - Special Stage (Sonic 1)
0x1405C - Oxigen (Sonic 1)  

FLOOR DEFINITIONS POINTERS

MISC. OPTIONS

0x38A - 0004 move to 0000 Start With Sega Logo.
0x1F30 - Palette Cicling Pointers
0x3926 - 0001 -> Enable / 0000 ->Disable  Level Select Menu
0x3D3B - First number in the Sound Test (80)
0x4CCA - Skip End Level art Settings
0x5BC8 - Bg Screen Size Pointers
0x5E16 - Bg Scrool Pointers
0x7A26 - Boss and Misc Settings Pointers
0x22408 - Animated Sprites (Load in Vram) Pointers
0x229A2 - Animated Sprites (Assembly) Pointers
0x23DBE - Debug Mode Pointers
0x50000 - Sonic Sprites (Uncompressed)
0x6254C - Tails Sprites (Uncompressed)