dev, computing and games

J. R. R. Tolkien’s Lord of the Rings for Super Nintendo shipped with a bug as you get toward the later parts of the game.

Short version: use these Pro Action Replay codes to un-glitch the late-game passwords.

81CBF10C
81A3900C
81A35C0C

Longer explanation below.

If you’re in Moria past the entrance and the first part and request a password, the game will give you one. However, if you write down and try to use that same password later, the game won’t accept it.

This is especially troublesome because

a) it’s in the most tedious part of the game, a part you wouldn’t ever want to re-do, and

b) even if you back-track to the Moria entrance, it won’t go back to giving you valid passwords. The game’s password system is basically cursed.

I investigated to understand this more. First, the password validation converts this character into a number.

The exact way it does this is described in an earlier post. So for here, L is 9, M would be 10, and so on.

Starting from there, I found out more by

  • typing a numerical garbage password like “023741” into the first six characters
  • taking memory dump of RAM
  • running a relative searcher on the memory dump, looking for a pattern like the one above
  • found one result. This was lucky in how the number was indeed stored in RAM- not written back to some reserved space of the ROM, and that I had picked a unique enough number
  • Used that to get the RAM address of the character boxed in red above
  • Set a break-on-read of that RAM address in the debugger
  • Breakpoint hit when you press the button for password confirm. This also, was a bit lucky. The game only read the password back for initial graphics or when you hit ‘confirm’. No reading it back continuously, no noisy breakpoints.
  • Stepped through in debugger to see what it did with the password character. When it copied the password character, set break-on-read of that too. This led to un-tangling the password characters from what I called the AreaNumbers below. I saved the code and marked it up with comments and labels.

Password validation calls this function

// Function: ReadPasswordLocationCode()
// Precondition: location code is stored at $81:039C
// Postcondition: result stored in 801CCB, 801CCD, 801CC9.
//   The result is what I'm calling an "AreaNumber"
//    plus positional information about
//    where in the world to load the player.
// 
//    Early-game AreaNumbers are high-numbered. 
//    Late-game ones are low.
//    Examples: 
//      Crossroads is 0x12A. 
//      Rivendell is 0x138. 
//      Moria Entrance is 0xEF. 
//      Moria 1 is 0x51. 
//      Moria 2 is 0x0C.

$81/CBEA B9 84 03    LDA $0384,y[$81:039C]   ; Load location code. E.g., the password 
                                             ; character 'M', which is 0xA

$81/CBED 29 1F 00    AND #$001F              ; Ignore upper bits 
$81/CBF0 C9 0A 00    CMP #$000A              						
$81/CBF3 90 02       BCC $02    [$CBF7]      ; If the password character is equal or greater than 
                                             ;'M' (0xA), fall through                                                                               
                                             ; to LocationCodeTooHigh.
                                             ; Otherwise, goto LocationCodeOk.

LocationCodeTooHigh:
$81/CBF5 38          SEC                     
$81/CBF6 6B          RTL                     ; Bail

LocationCodeOk:
$81/CBF7 85 90       STA $90    [$00:0090]   
$81/CBF9 A5 90       LDA $90    [$00:0090]   
$81/CBFB 0A          ASL A                  
$81/CBFC AA          TAX                     

// Write the output
$81/CBFD BF 18 CC 81 LDA $81CC18,x[$81:CC2A] 
$81/CC01 8F CB 1C 80 STA $801CCB[$80:1CCB]   
$81/CC05 BF 30 CC 81 LDA $81CC30,x[$81:CC42] 
$81/CC09 8F CD 1C 80 STA $801CCD[$80:1CCD]  
$81/CC0D BF 48 CC 81 LDA $81CC48,x[$81:CC5A] 
$81/CC11 8F C9 1C 80 STA $801CC9[$80:1CC9]   

$81/CC15 C8          INY                    
$81/CC16 18          CLC                     
$81/CC17 6B          RTL                     

It’s pretty easy to see the problem. It validates your location code is too high if you specify ‘M’ or ‘N’, but those are codes the game gives you. It was clearly a mistake. Changing the line

$81/CBF0 C9 0A 00    CMP #$000A

to

$81/CBF0 C9 0A 00    CMP #$000C

will fix it, allowing through AreaNumbers up to N (since a password character N = 11 = 0xB), the maximum the game will give you.

This unblocks the password validation code. But, if you were to patch the above change and try it, you’d see the screen fade but hang there forever soft-locked and not loading the level. So we’re not out of the woods yet.

The hang happens because we get past the password-validation and into level-loading yet there’s parts of the level loading code that block out AreaNumbers belonging to Moria.

We get here

// Function: AreaLoadStaging()
// Preconditions: Location codes have been written to 801CCB, 801CCD 801CC9
// Expected behavior: Sanitize out bad location codes (e.g., bad
//   AreaNumbers) and call a common function AreaHelper(). AreaHelper()
//   is a common channel used during both password-based loading and
//   normal level loading as you move from one place to another in the game.

$81/A377 E2 30       SEP #$30                
$81/A379 AF 0E 1D 80 LDA $801D0E   
$81/A37D CF 72 03 80 CMP $800372 
$81/A381 F0 76       BEQ $76     
$81/A383 AF 72 03 80 LDA $800372
$81/A387 30 70       BMI $70 
$81/A389 C2 20       REP #$20
$81/A38B AF C5 1C 80 LDA $801CC5          ; Load the area number.
										
$81/A38F C9 54 00    CMP #$0054   
$81/A392 B0 52       BCS $52    [$A3E6]   ; If area number < 54, fall through to 
                                          ; InvalidAreaNumber_TooLow.
                                          ; Otherwise, goto ValidAreaNumber.

InvalidAreaNumber_TooLow:
$81/A394 E2 20       SEP #$20              
$81/A396 AF 0E 1D 80 LDA $801D0E
$81/A39A C9 04       CMP #$04 
$81/A39C D0 0E       BNE $0E  
$81/A3AC E2 20       SEP #$20 
$81/A3AE A9 00       LDA #$00 
$81/A3B0 48          PHA     
$81/A3B1 AF 72 03 80 LDA $800372
$81/A3B5 48          PHA   
$81/A3B6 F4 06 00    PEA $0006 
$81/A3B9 22 02 80 81 JSL $818002
$81/A3BD 85 34       STA $34              ; Fall through into BadLoop

BadLoop:
$81/A3BF A9 00       LDA #$00 
$81/A3C1 48          PHA
$81/A3C2 AF 72 03 80 LDA $800372
$81/A3C6 48          PHA       
$81/A3C7 F4 06 00    PEA $0006  
$81/A3CA 22 02 80 81 JSL $818002
$81/A3CE C5 34       CMP $34   
$81/A3D0 F0 ED       BEQ $ED 
// This hangs forever :(

ValidAreaIndex:
$81/A3E6 E2 20       SEP #$20 
$81/A3E8 A9 00       LDA #$00 
//... clipped for brevity

It’s possible they originally intended for bad location codes to do something more elegant than a hang in this function (early out?). Or perhaps not, if they were sure this code wasn’t reachable.

Anyway, changing

$81/A38F C9 54 00    CMP #$0054

to

$81/A38F C9 0C 00    CMP #$000C 

fixes it here. The AreaNumbers for the last two levels are 0051 and 000C, so 0C covers it. The fact that it’s the same number as patched above is really a coincidence.

If you were to apply this change and run the game, you would still see the same symptom as before where the screen would fade to black yet no level would get loaded. This is because it gets further in the level-loading code before getting stuck again. It gets here

// Function: CallAreaLoadHelperArg4 ($81:A33A)
//  Preconditions: An AreaNumber is passed in through address $80:1CC5.
//  Expected result: Validate the AreaNumber.
//    If valid, push the argument '4' onto the stack and then call AreaLoadHelper(),
//    a common code path shared between password-loading usual traversal
//    through the game world.
$81/A33A E2 30       SEP #$30 
$81/A33C AF 0E 1D 80 LDA $801D0E
$81/A340 CF 72 03 80 CMP $800372
$81/A344 F0 2E       BEQ $2E 
$81/A346 AF 72 03 80 LDA $800372
$81/A34A 30 28       BMI $28 
$81/A34C C2 20       REP #$20 
$81/A34E AF C3 1C 80 LDA $801CC3
$81/A352 C9 EF 00    CMP #$00EF 
$81/A355 F0 09       BEQ $09
$81/A357 AF C5 1C 80 LDA $801CC5

$81/A35B C9 54 00    CMP #$0054            ; Load AreaNumber
$81/A35E 90 14       BCC $14    [$A374]    ; If too low, goto InvalidLocation. 
                                           ; If okay, fall through to ValidAreaNumber

ValidAreaNumber:
$81/A360 E2 20       SEP #$20  
$81/A362 A9 00       LDA #$00         
$81/A364 48          PHA           
$81/A365 AF 72 03 80 LDA $800372
$81/A369 48          PHA         
$81/A36A F4 00 01    PEA $0100  
$81/A36D F4 04 00    PEA $0004             ; Push args
$81/A370 22 02 80 81 JSL $818002[$81:8002] ; Call AreaLoadHelper()

InvalidLocation:
$81/A374 C2 30       REP #$30            
$81/A376 6B          RTL                  

Another place where the validation is on the wrong bounds.

So, change

$81/A35B C9 54 00    CMP #$0054 

to

$81/A35B C9 0C 00    CMP #$000C

allowing through both within-Moria area numbers, it works.

It is kind of good password-resuming the last two areas was something superficial like this, and not a deeper problem like a huge swath of level loading being actually not implemented. Well, the odds a “not implemented” would be low anyway since at least that part was written in a reasonable way- i.e., if you can visit an area, you can password-resume to it. They share the same code.

As for the fix since the total amount of changes is small, you could use a ROM patch, but it’s even easier as a cheat code like a Pro Action Replay code. Expressing the above changes as SNES Pro Action Replay the codes are

81CBF10C
81A3900C
81A35C0C

Because these are value changes to ROM code (where the game doesn’t self modify this code) you shouldn’t need to re-start the game to apply them.

Here is a demo of the codes in action

I was gonna post this to GameFaqs but they have this

oh well.

Anyway, you can use the cheat codes in any mainstream emulator (tested ZSNES, Snes9x) to unblock the game. Enjoy

April 6th, 2021 at 6:51 am | Comments & Trackbacks (0) | Permalink

This is an explanation of the formats of the password used in the game. I found this information by trying different passwords and seeing what is accepted by the game and what the effects were. Since this process didn’t involve a debugger it could have been done on the console, but using an emulator sped this up a lot.

This game has a hugely long password (48 characters.)

Each alphanumeric character is one of

 .BCDFGHJKLMNPQRSTVWXYZ0123456789

That’s a ‘.’, the letters of the alphabet with no vowels plus the numbers 0 through 9. This gives 32 choices in total.

The general layout of the password is: (where ‘.’ represents an alphanumeric character)

             Samwise   Merry           Frodo   Pippin    
            [       ][       ]       [       ][       ]  
             .  .  .  .  .  .         .  .  .  .  .  .   
                                                         
                                                         
                                                         
            Legolas   Aragorn          Gimli   Gandalf   
            [       ][       ]       [       ][       ]  
             .  .  .  .  .  .         .  .  .  .  .  .   
                                                         
                                                         
Spawn location              keys              Checksum   
            [ ][         and events          ][       ]  
             .  .  .  .  .  .         .  .  .  .  .  .   
                                                         
                                                         
                             Inventory                   
            [                                         ]  
             .  .  .  .  .  .         .  .  .  .  .  .   

As shown above there’s

  • 3 characters for each of the 8 people in the fellowship (Boromir isn’t joinable)
  • 1 character for your spawn location
  • 8 characters representing keys and events
  • 3 characters for checksum
  • and a 12-character inventory code at the bottom labeled ‘INVENTORY CODE’ in the password input screen.

Following goes into more detail for each of these.

Password characters

The alphanumeric password is a convenience (lol) for the user. Internally the game maps each character in a password to a number.
The mapping is this

Character | Value 
------------------
   .      |  0    
   B      |  1    
   C      |  2    
   D      |  3    
   F      |  4    
   G      |  5    
   H      |  6    
   J      |  7    
   K      |  8    
   L      |  9    
   M      |  10   
   N      |  11   
   P      |  12   
   Q      |  13   
   R      |  14   
   S      |  15   
   T      |  16   
   V      |  17   
   W      |  18   
   X      |  19   
   Y      |  20   
   Z      |  21   
   0      |  22   
   1      |  23   
   2      |  24   
   3      |  25   
   4      |  26   
   5      |  27   
   6      |  28   
   7      |  29   
   8      |  30   
   9      |  31  

In the sections that follow, these numerical representations of password characters get used and there is math done on them.

People in the fellowship

For each joinable person in the fellowship there’s a three-character code that encodes their level and equipment.

Firstly, if the three character code is all ‘.’ (value zeroes), that character is not in your party. Otherwise yes they are in your party.

The way in which the codes determine equipment is a bit convoluted and broken. The reason I say that is there are some
passwords that are accepted by the game but will either crash the game or cause corrruption while you’re playing. The charts and things below describe passwords which are accepted and also don’t crash or corrupt the game.

You can find situations (e.g., what if Code3, described below, is less than 16?) where the password gets accepted, the level gets loaded and things appear okay but corruption happens when you go into the menu for example. I reverse engineered what level/items you get in those cases too, and they’re accounted for in the source code of my password editor. I’m leaving them out of this document so that these formulas stay neat and concise as they’re specified, because those don’t follow the rules listed below. If you want you can see source code here for more info on them

So anyway, each person in the fellowship gets a three-character code in the password. Call the three characters in the code
Code1, Code2, and Code3 in order.

For example if the password contained ‘B89’ then Code1=1, Code2=30, Code3=31 referring to the chart above. Yes, each of
Code1, Code2 and Code3 is a number between 0 and 31 inclusive.

Level is decided by the following:

if (Code1 < 10)
	Level = (Code2 mod 8) * 20 + Code1
else
	Level = (Code2 mod 8) * 20 + (Code1 mod 16) + 10

The ‘mod’ operator here is modulus. I.e., A mod B is the remainder when A is divided by B.

Armor is decided by the following:

 PW char 2  |     Code2      | Armor                          
--------------------------------------------------------------
. through F |  0 through 4   | If Code3 is even, Cloth Cloak. 
            |                | If Code3 is odd, Plate Mail.   
--------------------------------------------------------------
. through F |  0 through 4   | If Code3 is even, Cloth Cloak. 
            |                | If Code3 is odd, Plate Mail.   
--------------------------------------------------------------
K through P |  8 through 12  | If Code3 is even, Padded Armor.
            |                | If Code3 is odd, Mithril Armor 
--------------------------------------------------------------
T through Y |  16 through 20 | Leather Armor                  
--------------------------------------------------------------
2 through 6 |  24 through 28   Chain Mail                     

Weapons are decided by the following:

PW char 3| Code3 | Weapon        
 ----------------------------  
  T      |  16   | Old Dagger    
  V      |  17   | Old Dagger    
  W      |  18   | Dagger        
  X      |  19   | Dagger        
  Y      |  20   | Barrow Dagger  
  Z      |  21   | Barrow Dagger  
  0      |  22   | Troll Dagger  
  1      |  23   | Troll Dagger  
  2      |  24   | Elvish Dagger  
  3      |  25   | Elvish Dagger  
  4      |  26   | Sting         
  5      |  27   | Sting         
  6      |  28   | Light Sword   
  7      |  29   | Light Sword   
  8      |  30   | Sword         
  9      |  31   | Sword   

The password encoding for level, weapon and armor works the same for each of the 8 joinable characters.

Fun fact: if you enter an only-partially-valid password that includes some configuration for a character (e.g., the string is not all ‘.’), it permanently adds the character to your party until SNES reset. Even if the password is rejected. This leads to a well-known cheesy trick where you can enter a bad password, press start and hear the “invalid password” noise, then delete it and start the game with all the Fellowship unlocked.

Spawn Location

This is the place in the game world your party will be in after the password gets accepted.
It’s a 1-character code.

PW char| Code | Location             
-------|------|------------          
  .    |  0   | Hobbiton             
  B    |  1   | Brandywine Bridge    
  C    |  2   | Farmer Maggot        
  D    |  3   | Ferry                
  F    |  4   | Crickhollow          
  G    |  5   | Tom Bombadil's House 
  H    |  6   | Barrow Downs Stones  
  J    |  7   | Crossroads           
  K    |  8   | Rivendell            
  L    |  9   | Moria entrance       
  M    |  10  | Moria 1 (glitched)   
  N    |  11  | Moria 2 (glitched) 

For the last two Moria locations, the game will include those location codes in the passwords it provides to you when you’re in Moria.

However, it won’t accept the passwords the next time you start the game 🙁

Might want to keep a map of Moria, you definitely don’t want to do it more than once if you can help it

Keys and events

These control the state of various unlockable doors and questlines. I haven’t reverse-engineered which bits control what.

Checksum

The checksum exists to stop you from trying random passwords and cheating. It’s a way of making sure the only passwords accepted are ones the game has actually given to you, not ones you randomly made up yourself.

However, the checksum is pretty easy to understand if you look at the various passwords it gives you. For example, you’ll see that leveling up or changing equipment only changes the first character. And using something in your inventory only changes the third character. And, you know how the password characters translate to character codes and there are 32 of them, and modulus kinds of operations are common and inexpensive for computing checksums.

The first character is the ‘party checksum’:
partySum = the sum of the character codes of the first two lines of the password
checksumCode = remainder when partySum is divided by 32. (For example, if partySum is 33, the checksumCode is 1.)

The second character is the ‘event checksum’:
eventSum = the sum of the character codes in the “spawn location” and “keys and events” part of the password
checksumCode = remainder when eventSum is divided by 32

The third character is the ‘inventory checksum’:
inventorySum = the sum of the character codes in the “inventory” part of the password
checksumCode = remainder when inventorySum is divided by 32

This gives you the first, second and third characters of the checksum in order.

I think they put the checksum in the middle of the password to obfuscate it a little bit.

If you’re trying to troubleshoot, know that valid checksum doesn’t necessarily mean the password will be accepted. The game sometimes rejects passwords for reasons other than invalid checksum. For example, if you specify an invalid location code like ‘Z’.

Inventory

These character codes store your inventory state pretty compactly.
Each item corresponds to 1 bit within a byte. Not all the bits are used, which is why a full inventory’s password code looks like “9S9S9S 9S9S9S” rather than all 9s (all 9s means all bits set).

There are 12 inventory code characters in all, which I’m calling code 0 through 11.

For readability the bit is written as a hexadecimal flag.

Item                |Code #| Bit      
--------------------------------    
Tomb Key            |  0   | 0x1      
Moria Key           |  0   | 0x2      
Red Gateway Gem     |  0   | 0x4      
Elvish Book         |  0   | 0x8      
Magic Rock          |  0   | 0x10     

Bottle              |  1   | 0x1      
Lost Amulet         |  1   | 0x2      
Maggot Note         |  1   | 0x4      
Scroll Of Floi      |  1   | 0x8      

Gate Key            |  2   | 0x1      
Moria Key           |  2   | 0x2      
Yellow Gateway Gem  |  2   | 0x4      
Book Of The Ages    |  2   | 0x8      
Gold Piece          |  2   | 0x10     

Jug Of Honey        |  3   | 0x1      
Lost Amulet         |  3   | 0x2      
Old Willow Note     |  3   | 0x4      
Scroll Of Oin       |  3   | 0x8      

Tomb Key            |  4   | 0x1      
Moria Key           |  4   | 0x2      
Gateway Keystone    |  4   | 0x4      
Book Of Mazarbul    |  4   | 0x8      
Gold Pieces         |  4   | 0x10     

Eye Glasses         |  5   | 0x1      
Lost Amulet         |  5   | 0x2      
Note From Gandalf   |  5   | 0x4      
Color Scoll         |  5   | 0x8      
Item                |Code #| Bit 
---------------------------------
Tomb Key            |  6   | 0x1 
Moria Key           |  6   | 0x2 
Green Gateway Gem   |  6   | 0x4 
Bilbo Diary         |  6   | 0x8 
Gold Pieces         |  6   | 0x10

Healing Moss        |  7   | 0x1 
Lost Amulet         |  7   | 0x2 
Letter To Elrond    |  7   | 0x4 
Keystone Scroll     |  7   | 0x8 

Tomb Key            |  8   | 0x1 
Boat Oar            |  8   | 0x2 
Purple Gateway Gem  |  8   | 0x4 
Jeweled Ring        |  8   | 0x8 
Gold Pieces         |  8   | 0x10

Athelas Major       |  9   | 0x1 
Lost Amulet         |  9   | 0x2 
Horn Of Boromir     |  9   | 0x4 
Long Bow            |  9   | 0x8 

Key To Bree         |  10  | 0x1 
Healing Mushroom    |  10  | 0x2 
Violet Gateway Gem  |  10  | 0x4 
The Ring            |  10  | 0x8 
Athelas Minor       |  10  | 0x10

Healing Fruit       |  11  | 0x1 
Lost Amulet         |  11  | 0x2 
Magic Fern          |  11  | 0x4 
Orb of Drexle       |  11  | 0x8 

The inventory codes come from bitwise OR-ing the corresponding bits together for each inventory item you have.

For example, suppose you have the first tomb key and the red gateway gem. This is bit ‘0x1’ and ‘0x4’. When you bitwise-OR these, you get ‘5’. Code 5 corresponds to password code ‘G’, from the chart all the way at the top. So if those two are the only items you have, your inventory code in the password is ‘G….. ……’.

For another example, suppose all you have is the first tomb key and the Orb of Drexle. This is bit ‘0x1’ of the first code, and ‘0x8’ of the last. So if those were the only two items you have, your inventory code in the password is ‘B….. …..K’.

There’s one special case- although there’s an inventory bit allocated to the One Ring, the ring is always in your inventory regardless of whether it’s encoded in the password or not.

Links

Hope you found this helpful

All this information is used in a password editor I made. That is here
https://github.com/clandrew/lotrpwcheck/

To view this post in text form, it’s here
https://raw.githubusercontent.com/clandrew/lotrpwcheck/master/Format.txt

This post is following up from this one where I posted the editor, where someone asked about the information that the editor uses

March 31st, 2021 at 5:25 am | Comments & Trackbacks (1) | Permalink

This post describes how to change players’ names arbitrarily (longer or shorter) in the game NHL ’94 for Super Nintendo by changing the ROM.

Players’ names are shown as text in the menus and in-game.

In the team selection menu, it’s their first initial and last name. In other places, it’s the full first and last name.

Goal is to change how names appear in all these places. Have new names’ length be allowed to be different from the old names.

My own intended usage for this is to only change a few names, so optimize for that. And optimize for game stability because I plan to play the game, not just do a quick demo. I don’t care if the result is not elegant or wasteful in terms of memory. The result can operate on an expanded ROM.

The Very Easy, Very Limited Way

Easiest way to change names is a pure data hack. Doesn’t require any knowledge about SNES at all, only basic computer literacy. Open the ROM in a hex editor such as HxD. Scroll down until you see players’ names on the right, and type over them. Hit Ctrl+S to save. Start your game and go.

Why does this work? Because all player names are literally stored as ASCII, no need for character translation tables or whatever. Also, each name is only stored in 1 place.

But of course, the catch is whatever new name you pick has to be the same length or shorter. Ideally, the same length. Shorter only kind of works because you can pad names with spaces, but no guarantees that’ll look right when you see it laid out on the screen. And if the new name is longer it definitely won’t work. Since the goal is to let you change names without length restrictions we have to do something more.

The reasons why you can’t change the name length as a pure data hack take some context to explain. So they are explained further down. The first thing you need to know is the data you just tried to hack- what is it, really.

Player-data Format

This describes where and how players’ names are stored in the ROM, as well as the neighboring data.

There is what I’m calling a “main pointer table”. The table has 28 values. This table is stored at ROM address 0x9CA5E7.

If you dump the raw data for the table it’s

 	4F EB 9C 00 AC AB 9C 00 32 AE 9C 00 C1 B0 9C 00
 	40 B3 9C 00 4F C0 9C 00 D7 B5 9C 00 9D B8 9C 00
 	4D E9 9C 00 1D BB 9C 00 B2 BD 9C 00 DB C2 9C 00
 	7E C5 9C 00 2B C8 9C 00 9C CA 9C 00 06 CD 9C 00
 	AC CF 9C 00 37 D2 9C 00 D2 D4 9C 00 60 D7 9C 00
 	D4 D9 9C 00 4A DC 9C 00 DC DE 9C 00 7E E1 9C 00
 	AD E6 9C 00 05 E4 9C 00 57 A6 9C 00 04 A9 9C 00

Formatted nicely, the table is

int mainTable[] = { 
    9CEB4F, // Anaheim
    9CABAC, // Boston
    9CAE32, // Buffalo
    9CB0C1, // Calgary
    9CB340, // Chicago
    9CC04F, // Dallas
    9CB5D7, // Detroit
    9CB89D, // Edmonton
    9CE94D, // Florida
    9CBB1D, // Hartford
    9CBDB2, // LA Kings
    9CC2DB, // Montreal
    9CC57E, // New Jersey
    9CC82B, // NY Islanders
    9CCA9C, // NY Rangers
    9CCD06, // Ottawa
    9CCFAC, // Philly
    9CD237, // Pittsburgh
    9CD4D2, // Quebec
    9CD760, // San Jose
    9CD9D4, // St Louis
    9CDC4A, // Tampa Bay
    9CDEDC, // Toronto
    9CE17E, // Vancouver
    9CE6AD, // Washington
    9CE405, // Winnepeg
    9CA657, // All Stars East
    9CA904  // All Stars West
};

There is 1 value per hockey team.
The first element in the array belongs to Anaheim, and the value is 0x9CEB4F.
The second element in the array belongs to Boston, and the value is 0x9CABAC, and so on.

The teams are ordered alphabetically, except for the all-stars teams at the end. The values themselves aren’t in any particular order.

Although the all-stars teams are comprised of players which exist on other teams, they have their own entries in the table. That’s the game opting for perf and simplicity of code in the perf-memory tradeoff.

Looking at the values of elements in this array, you might think they also look like ROM addresses and you would be right.
As for what’s stored at each address- here’s a description

[H0] [H1] [some number of header bytes] // A two-byte low-endian length H, and a variable-length 
                                        // header stream of length H-2

For each player:
[L0] [L1] [player's name]     // A two-byte low-endian length L, and then a variable-length string 
                              // of length L-2

[PlayerNumber]                // A byte for the player number. It's in a decimal format.
                              // Leftmost half-byte is the tens place value. Rightmost half-byte is 
                              // the ones place value.

[WeightClass, Agility]        // A byte. Leftmost half-byte is the player's weight class. 
                              // Rightmost half-byte is their agility rating.
                              // Weight class is displayed as a measurement in pounds when 
                              // displayed on the team roster page.
                              // To convert from weight class to pounds, it's 
                              // 	pounds = 140 + (weightClass * 8)
                              // Weight classes range from 0 to 14 in practice. Higher numbers may 
                              // be hacked.
                              // Agility rating is from 0 to 6.
                          
[Speed, OffenseAware]         // A byte. Leftmost half-byte is player's speed. Rightmost half-byte 
                              // is their offense awareness rating.
                              // Ratings are from 0 to 6.
                          
[DefenseAware, ShotPower]     // A byte. Leftmost half-byte is player's defense awareness rating. 
                              // Rightmost half-byte is their shot power.
                              // Ratings are from 0 to 6.
                          
[Checking, Handedness]        // A byte. Leftmost half-byte is player's checking rating. Rightmost 
                              // half-byte is their handedness.
                              // Checking rating is from 0 to 6.
                              // For handedness, if the value is even (divisible by 2) they shoot 
                              // left. If it's odd they shoot right.
                          
[StickHandling, ShotAccuracy] // A byte. Leftmost half-byte is player's stick handling rating. 
                              // Rightmost half-byte is their shot accuracy.
                              // Ratings are from 0 to 6.
                          
[Endurance, Roughness]        // A byte. Leftmost half-byte is player's endurance rating. Rightmost 
                              // half-byte is their 'roughness' rating.
                              // Ratings are from 0 to 6.
                              // The 'roughnesss' stat is a hidden stat. It exists but is not 
                              // displayed in the game or the manual.
                              

[PassAccuracy, Aggression]    // A byte. Leftmost half-byte is player's pass accuracy rating. 
                              // Rightmost half-byte is their aggression rating.
                              // Ratings are from 0 to 6.

Then, at the end:

[00] [00]		      // Two zero bytes mean that's the end of the player data for this 
                              // team.

For example, if we dereference and dump what’s stored at 9CC2DB (Montreal), we get

55 00 0E 00 79 02 1D 00 0E 00 13 00 15 00 52 11
21 E8 49 C5 00 01 12 11 07 03 0C 04 00 01 17 12
07 03 0C 04 00 01 16 11 08 04 0E 03 00 01 13 14
09 05 0D 03 00 01 12 11 07 03 0C 05 00 01 13 14
08 04 05 03 00 01 11 17 07 06 03 0D 00 01 16 13
03 0D 07 06 00 0D 00 50 61 74 72 69 63 6B 20 52
6F 79 33 66 44 46 00 00 55 66 ...

Cleaned up, this is

Cleaned up, this is

headerSize = 0x0055;
byte header[] = {0E 00 79 02 1D 00 0E 00 13 00 15 00 52 11
                 21 E8 49 C5 00 01 12 11 07 03 0C 04 00 01 17 12
                 07 03 0C 04 00 01 16 11 08 04 0E 03 00 01 13 14
                 09 05 0D 03 00 01 12 11 07 03 0C 05 00 01 13 14
                 08 04 05 03 00 01 11 17 07 06 03 0D 00 01 16 13
                 03 0D 07 06 00 };

player0 = {
    // L0 L1 P  a  t  r  i  c  k  __ R  o  y
       0D 00 50 61 74 72 69 63 6B 20 52 6F 79 // "Patrick Roy" 
                                              // 11 character length + 
                                              // 2 byte string size = 13 = 0xD, converted to 
                                              // two-byte low endian that's 0D 00    
       33 // Number 33 
       66 // Weight class 6, agility 6                                    
       44 // speed 4, OffAware 4
       46 // DefAware 4, shot power 6
       00 // checking 0, handedness L
       00 // stick handling 0, shot accuracy 0
       55 // endurance 5, roughness 5
       66 // pass accuracy 6, aggression 6
}

Etc, for the rest of the players. Then there are some team-related strings at the end.

Heads up that viable (e.g., a subsequent team’s) game data can follow immediately after the data for each team. So no, you’re not free to grow things off the end.

Side thing: stats stored affect the stats in-game although you’ll notice they don’t correlate to those stats exactly. That’s because each game applies RNG. Try it yourself if you want. Boot the game, pick two teams and look at a player’s stats. Reset the game, pick the exact same matchup and player to look at. The stats will be slightly different. If you play a lot of sports games maybe this is not surprising. There is this real-world idea that any team could potentially beat any other team.

Strings are stored with a length rather than being delimited, so that’s nice. However, there’s a bunch of player data parsing code that needs to skip over player’s names to get to their stats. So if you make a player’s name shorter, you’d need to either pad with spaces (could cause things to display weirdly) or update the length value and move that person’s stats plus everyone else on the team’s data backwards. I’ve listed all the stats out because you need to know how much to move if you do it that way, and it’s also helpful to know what it is you’re moving.

And of course for making player’s names longer, there isn’t any extra space off the end, so you need something else entirely. This was the case I was more interested in.

Why not move the whole team data, and update the “main pointer table” entry?

This seemed like a swell idea at first. To get names as long as you want, just make a totally new copy of the player data someplace else with your new names, then adjust the “main pointer table” value to point to it.

Unfortunately that won’t work. It is true the “main table” above is a table of long (four-byte) pointers. But, the upper two bytes of each entry are either

  • dead data, sometimes
  • dead data, always

By “dead data” I mean the data isn’t read and doesn’t do anything.

Instead of reading data from the upper two bytes, the game will use a hardcoded number which is $9C.

Here’s an example of what I mean. This is from the code to figure out a player’s first initial and last name for the team selection screen.

			                      ; Precondition: 9F1CDC and $9f1CDE have been 
                                              ; initialized with 
			                      ; main table elements for home and away teams 
                                              ; respectively.
			                      ; We're in 16-bit mode.
			                      ;
$9F/C732 A9 9C 00    LDA #$009C               ; Hardcode $9C in the upper part
$9F/C735 85 8B       STA $8B
$9F/C737 A4 91       LDY $91
$9F/C739 B9 DC 1C    LDA $1CDC,y[$9F:1CDC]    ; Load the short pointer from the main table
$9F/C73C 85 89       STA $89                  ; Store the short pointer in the lower part
                                              ;
                                              ; ... do stuff that uses direct addressing on 
                                              ; 24-bit pointer. For example, ADC [$89].    

There are multiple instances of this pattern. I found several without trying super hard and I believe there are more. If you want to change a “main pointer table” entry, you don’t just change the entry- you need to change some undetermined number of places in game code.

Why store long pointers in the table if they were gonna do it this way? They could have just stored short pointers. Seems like a waste of space. It might have been, they started out planning for long pointers but wanted to optimize reading/dereferencing of the table values, then they never tried to go back and shrink the table.

Anyway, it’s hard to safely detect all the places that pull values out of this table so it’s difficult to “fix” the table and reclaim the space. I didn’t try. If you want to try it to be absolutely safe you might want to set a breakpoint in the debugger and play the game extensively. We don’t have source code and you can’t statically disassemble this platform.

So suppose you begrugingly accept the fact that all table entries need to live in bank $9C. Can you change lower bytes only and make that work? Unfortunately that’s not such a good idea either. You can adjust these table values to point someplace else in bank $9C, but there isn’t all kinds of free space in that bank to put anything.

If we want to move player data (including player names’ string data) to a different location in memory, a different bank- I prefer a safer option that is more targeted. Completely bypass the use of the “main pointer table” entry JUST when we are loading player names. This lets us be really confident in things working. We make a code change in a specific, testable place that we understand really well.

Detouring the loading of player names

NHL ’94 has a function I’m calling LookupPlayerName().

The code for LookupPlayerName() is

                                             ; Function: LookupPlayerName()
                                             ;     Gets the address of a player's name string, 
                                             ; based on the player's index on the team and some 
                                             ; previously-set table data.
                                             ;
                                             ; Preconditions: 
                                             ;     $91 contains HomeOrAway. 0 == home, 2 == away
                                             ;     $9F1CDC and $9F1CDE have been initialized with 
                                             ;     main table elements for home and away teams 
                                             ; respectively.
                                             ;     $A5 contains PlayerIndexOnTeam
                                             ;
                                             ; Postconditions:
                                             ;     $89-$8B = Address of the player's name string
                                             ; data. (Includes the length field that comes first)
                                             ;
                                             ; $A5 gets scrambled.

$9F/C732 A9 9C 00    LDA #$009C              ; Hardcode 9C in the upper bytes. Easy enough.                                              
$9F/C735 85 8B       STA $8B    [$00:008B]   ; 
                                             ;
$9F/C737 A4 91       LDY $91    [$00:0091]   ; Load the choice of HomeOrAway. 0 == home, 2 == away
$9F/C739 B9 DC 1C    LDA $1CDC,y[$9F:1CDC]   ; Load PlayerNamesStartAddress for the corresponding 
                                             ; team.
                                             ; As mentioned in the preconditions this has been set 
                                             ; up for us. As it happens, it's somewhere far away in 
                                             ; the chain of function calls.                                             
$9F/C73C 85 89       STA $89    [$00:0089]   ; And then store the lower bytes.																				

LookupPlayerName_GetOffsetOfPerPlayerData:
$9F/C73E A0 00 00    LDY #$0000              
$9F/C741 18          CLC                     
$9F/C742 67 89       ADC [$89]  [$9C:C2DB]   ; Use the fact that the first two bytes of the 
                                             ; PlayerNamesStartAddress
                                             ; data will give us the offset to the per-player data. 

$9F/C744 85 89       STA $89    [$00:0089]   ; For example, for Montreal we add 0x55 to get to the 
                                             ; start of the per-player data.

$9F/C746 80 0A       BRA $0A    [$C752]      ; Goto LookupPlayerName_CheckDone

LookupPlayerName_ForEachPlayerIndexOnTeam:
$9F/C748 A5 89       LDA $89    [$00:0089]   ; Load the length of the player's name.
$9F/C74A 18          CLC                     
$9F/C74B 67 89       ADC [$89]  [$9C:C330]   ; Increment the current $89-$8B pointer by the length
$9F/C74D 69 08 00    ADC #$0008              ; Plus 8, it's padding (Not really but let's pretend 
                                             ; it is)
$9F/C750 85 89       STA $89    [$00:0089]   ; Update the current $89-$8B pointer

LookupPlayerName_CheckDone:
$9F/C752 C6 A5       DEC $A5    [$00:00A5]   
$9F/C754 10 F2       BPL $F2    [$C748]      ; branch-if-positive
                                             ;  LookupPlayerName_ForEachPlayerIndexOnTeam

$9F/C756 6B          RTL

The idea is to detour this function. Use an “alternate main table” which actually does honor the long pointer, and shim LookupPlayerName() to use the “alternate main table” instead. From testing I found that LookupPlayerName() is a centralized place and changing it is sufficient.

How the detouring goes is we chuck a payload someplace there’s space (say, $A08100, in expanded ROM space). Then replace the code for LookupPlayerName() with

$9F/C732 5C 00 81 A0 JMP $A08100                ; Jump into expanded ROM space where we put the 
                                                ; detour payload
                     NOP
                     NOP
                     ...

NOPs are not strictly needed but added for hygiene. (Could use a BRK instead when you are getting things running)

As for the payload itself, it’s

$A0/8100 DA          PHX                        ; Caller doesn't like it if X is scrambled                  
         A4 91       LDY $91                    ; Load the team index, which has been stored at 
                                                ; 9F1C98/9F1C9A for home/away.
         B9 98 1C    LDA $1C98, y[$9F:1C98]
                                                
         0A          ASL                        ; Multiply by 4 to turn index into an offset
         0A          ASL                                               
                                                
         AA          TAX                        ; Use the team index to look up into the 
                                                ; "alternate main table".
         BF 00 D0 A8 LDA 0xA8D000,x             ; Load the array element from 0xA8D000, store it in 
                                                ; $89-$8C
         85 89       STA $89
         E8          INX
         E8          INX
         BF 00 D0 A8 LDA 0xA8D000,x
         85 8B       STA $8B

                                                ; The "alternate main table" is formatted a bit 
                                                ; differently from the "main table".
                                                ; Each element is itself an array, one four-byte 
                                                ; element per player.
                                                ; Use $A5 as a counter to get to the right player.

PlayerIndexIncrement:
        A5 A5        LDA $A5                    ; Sets Z
        F0 0C        BEQ $0C                    ; goto DonePlayerIndex

        E6 89        INC $89
        E6 89        INC $89
        E6 89        INC $89
        E6 89        INC $89
        C6 A5        DEC A5
        80 F0        BRA $F0                    ; goto PlayerIndexIncrement

DonePlayerIndex:
                                                ; We have the element for the right player stored 
                                                ; at $89-$8C.
                                                ; The element is a pointer. 
                                                ; It'll be either $9Cxxxx if we're keeping the 
                                                ; original names, or $A8xxxx/whatever if 
                                                ; we're using new names.
                                                ; Dereference it, and store the dereferenced result 
                                                ; at $89-$8C.
        A7 89        LDA [$89]
        48           PHA
        E6 89        INC $89
        E6 89        INC $89
        A7 89        LDA [$89]
        85 8B        STA $8B
        68           PLA
        85 89        STA $89

        FA           PLX                        ; Restore X and return.
        6B           RTL

One thing that allows the detour to work is there’s nothing in the detour that requires execution out of bank $9F (bank $9F is where the original function is). It’s okay if the code executes in bank $A8. And by a stroke of good fortune, it happens that the original code is also okay running from other banks. No absolute short addressing (local bank). This is hugely helpful when getting things up and running.

The “alternate main table” lives at 0xA8D000, chosen arbitrarily.

If this code were a bit smaller it could actually be copied overtop the implementation of LookupPlayerName() with no jumping out. Original LookupPlayerName is 37 bytes, this routine is 55 bytes. Alas, it won’t fit, so I put it at $A08100. Not a big deal since we are putting stuff in expanded ROM space anyway.

Putting it all together, the full list of things to patch are

  • the JMP at the beginning of LookupPlayerName
  • code snippet above it’s supposed to JMP to
  • the “alternate main table” at 0xA8D000 and set of tables each of its entries points to
  • the strings that the “alternate main table” points to

Not too bad.

Could do all this manually. I suggest making a program to do it so that you don’t make mistakes. And plus you can easily configure whatever new player names you want. I made an editor that does the above.

Example in the editor:

Patched game result

Enjoy

Download the editor here:

https://github.com/clandrew/nhl94e/releases/tag/v1.0

Or, find the editor source code here

https://github.com/clandrew/nhl94e

Find this post, in text form here:

https://raw.githubusercontent.com/clandrew/nhl94e/main/docs/PlayerNames.txt

November 23rd, 2020 at 6:07 am | Comments & Trackbacks (2) | Permalink

This post explains Lagoon_hitbox.ips, a proof-of-concept patch created to enlarge the hitboxes in the game Lagoon for SNES. The patch was really quick+and+dirty. Nonetheless it’s posted here:

http://secretplace.cml-a.com/edits.php

What follows is a description of the patch and how it works.

First, here are some useful memory locations

$01:0502-0503 - NASIR's X position in the map
$01:0504-0505 - NASIR's Y position in the map
$01:050A- The direction NASIR is facing.
	- 00 means right
	- 01 means down
	- 02 means left
	- 03 means up
	
$01:B710-B717 - The offsets of NASIR's hit box from his position, if he is facing right
$01:B718-B71F - The offsets of NASIR's hit box from his position, if he is facing down
$01:B720-B727 - The offsets of NASIR's hit box from his position, if he is facing left
$01:B728-B730 - The offsets of NASIR's hit box from his position, if he is facing up

In Lagoon, the following code is invoked whenever an action button is pressed, even if you’re not near anything.

$01/9BBD AD 0A 05    LDA $050A               ; A = the direction NASIR is facing.
					     ; 
$01/9BC0 0A          ASL A                   ; A *= 8
$01/9BC1 0A          ASL A                   ;
$01/9BC2 0A          ASL A                   ;
$01/9BC3 18          CLC                     ;
$01/9BC4 69 20       ADC #$20                ; A += 0x20
					     ; 
					     ; Now A effectively stores an array index with 
					     ; which to load hitbox offsets.
					     ; If facing right: A = 0x20
					     ; If facing down: A = 0x28
					     ; If facing left: A = 0x30
					     ; If facing up: A = 0x38
					     ; 
$01/9BC6 20 C3 B6    JSR $B6C3	             ; Call CalculatePlayerHitboxDimensions()
$01/9BC9 60          RTS                                         

The function CalculatePlayerHitboxDimensions() looks like the following

CalculatePlayerHitboxDimensions:
					     ; Preconditions: A is set to one of 
					     ;     {0x20, 0x28, 0x30, 0x38} depending on
					     ;     the direction NASIR is facing, as described 
					     ;     above.
					     ; Postconditions: $40, $42, $44, and $46 contain 
					     ;     the dimensions of NASIR's hit box; left, 
					     ;     right, top and bottom respectively.
$01/B6C3 C2 20       REP #$20                
$01/B6C5 A8          TAY                     
$01/B6C6 AD 02 05    LDA $0502               ; Load NASIR's X position
$01/B6C9 18          CLC                    
$01/B6CA 79 F0 B6    ADC $B6F0,y             ; Add left edge hitbox offset to NASIR's X position
$01/B6CD 85 40       STA $40                 ; Store it as an output
					     ; 
$01/B6CF AD 02 05    LDA $0502 		     ; Load NASIR's X position
$01/B6D2 18          CLC                     
$01/B6D3 79 F2 B6    ADC $B6F2,y             ; Add right edge hitbox offset to NASIR's X position
$01/B6D6 85 42       STA $42                 ; Store it as an output
					     ; 
$01/B6D8 AD 04 05    LDA $0504               ; Load NASIR's Y position
$01/B6DB 18          CLC   
$01/B6DC 79 F4 B6    ADC $B6F4,y             ; Add top edge hitbox offset to NASIR's Y position
$01/B6DF 85 44       STA $44                 ; Store it as an output
					     ; 
$01/B6E1 AD 04 05    LDA $0504               ; Load NASIR's Y position
$01/B6E4 18          CLC                     
$01/B6E5 79 F6 B6    ADC $B6F6,y             ; Add bottom edge hitbox offset to NASIR's Y position
$01/B6E8 85 46       STA $46                 ; Store it as an output
					     ; 
$01/B6EA 29 FF 00    AND #$00FF              ; Clean up and return
$01/B6ED E2 20       SEP #$20                
$01/B6EF 60          RTS          

If you were to skim the code quickly you’d see it loads hitbox dimensions from memory. From that, you might get the impression they are something dynamic. But, they come from a table hard-coded in ROM data. (you can see this based on the particular address they’re loaded from).

Just so you know, the hitbox table data contains this (Semantics are left, right, top, bottom)

Facing  	Raw data			Plain hex offsets		Signed dec offsets	
------		--------			-----------------		------------------
Right		00 00 19 00 F8 FF 08 00		0h, 19h, FFF8h, 8h		0, 25, -8, 8		
Down		F0 FF 10 00 00 00 0F 00		FFF0h, 10h, 0h, 0Fh		-16, 16, 0, 15	
Left		E7 FF 00 00 F8 FF 08 00		FFE7h, 0h, FFF8h, 8h		-25, 0, -8, 8
Up		F0 FF 10 00 F1 FF 00 00		FFF0h, 10h, FFF1h, 0h		-16, 16, -15, 0	

Yes, the game uses slightly differently-sized hitboxes depending on the direction you’re facing.

Now, the patch. What this patch does is instead of offsetting NASIR’s position by values from this table, it hacks it to offset the position simply by a hardcoded number. The hardcoded numbers yield bigger hitboxes than the offsets from the table.

It always applies the hitbox of offsets {-0x30, 0x32, -0x38, 0x30 } = {-48, 50, -56, 48 }. The hitbox size is 98×104 which is about 5 times bigger than the default.

The patch modifies just four operations in CalculatePlayerHitboxDimensions:

CalculatePlayerHitboxDimensions:
					     ; Preconditions: A is set to one of {0x20, 0x28, 0x30, 0x38} depending on
					     ;     the direction NASIR is facing, as described above.
					     ; Postconditions: $40, $42, $44, and $46 contain the dimensions of 
					     ;     NASIR's hit box; left, right, top and bottom respectively.
$01/B6C3 C2 20       REP #$20                
$01/B6C5 A8          TAY                     
$01/B6C6 AD 02 05    LDA $0502               ; Load NASIR's X position
$01/B6C9 18          CLC                    
$01/B6CA E9 30 00    SBC #$0030              ; Apply left edge hitbox offset -30h
$01/B6CD 85 40       STA $40                 ; Store it as an output
					     ; 
$01/B6CF AD 02 05    LDA $0502 		     ; Load NASIR's X position
$01/B6D2 18          CLC                     
$01/B6D3 69 32 00    ADC #$0032              ; Apply left edge hitbox offset 32h
$01/B6D6 85 42       STA $42                 ; Store it as an output
					     ; 
$01/B6D8 AD 04 05    LDA $0504               ; Load NASIR's Y position
$01/B6DB 18          CLC   
$01/B6DC E9 38 00    SBC #$0038              ; Apply left edge hitbox offset -38h
$01/B6DF 85 44       STA $44                 ; Store it as an output
					     ; 
$01/B6E1 AD 04 05    LDA $0504               ; Load NASIR's Y position
$01/B6E4 18          CLC                     
$01/B6E5 69 30 00    ADC #$0030              ; Apply left edge hitbox offset 30h
$01/B6E8 85 46       STA $46                 ; Store it as an output
					     ; 
$01/B6EA 29 FF 00    AND #$00FF              ; Clean up and return
$01/B6ED E2 20       SEP #$20                
$01/B6EF 60          RTS     

And there you have it, the code for the proof-of-concept posted at the link above.


Here is a small improvement that can be made to the above hack. First, it’d be cleaner to modify the hitbox region offsets in the ROM directly. So let’s do that instead.

To re-iterate, the default values are (with semantics left, right, top, bottom)-

Facing  	Raw data			Plain hex offsets		Signed dec offsets	
------		--------			-----------------		------------------
Right		00 00 19 00 F8 FF 08 00		0h, 19h, FFF8h, 8h		0, 25, -8, 8	
Down		F0 FF 10 00 00 00 0F 00		FFF0h, 10h, 0h, 0Fh		-16, 16, 0, 15	
Left		E7 FF 00 00 F8 FF 08 00		FFE7h, 0h, FFF8h, 8h		-25, 0, -8, 8	
Up		F0 FF 10 00 F1 FF 00 00		FFF0h, 10h, FFF1h, 0h		-16, 16, -15, 0	

The ROM file offsets for each direction are

Facing		Headerless ROM file offset
------		--------------------------
Right		B710
Down		B718
Left		B720
Up		B728

While we can patch the table manually, it makes for easier testing of changes if you use a patching program.

Here’s some C++ code for one:

enum Direction 
{ 
    FacingRight = 0, 
    FacingDown = 1,
    FacingLeft = 2, 
    FacingUp = 3 
};

struct HitboxDir
{
    int Left;
    int Right;
    int Top;
    int Bottom;
};

void PushValue(int b, std::vector<unsigned char>* out)
{
    if (b >= 0)
    {
        assert(b < 256);
        out->push_back(b); // little endian
        out->push_back(0);
    }
    else
    {
        int u = 0x10000 + b;
        int low = u & 0xFF;
        out->push_back(low);
        u >>= 8;
        assert(u < 256);
        int high = u & 0xFF;
        out->push_back(high);
    }
}

int main()
{
    FILE* pB = nullptr;

    fopen_s(&pB, "Lagoon.hitbox.v2.smc", "rb");

    // Check size
    fseek(pB, 0, SEEK_END);
    long sizeB = ftell(pB);
    fseek(pB, 0, SEEK_SET);

    std::vector<unsigned char> dataB;
    dataB.resize(sizeB);

    fread(dataB.data(), 1, sizeB, pB);

    fclose(pB);

    HitboxDir allDirs[] =
    {
        {0, 25, -8, 8},
        {-16, 16, 0, 15},
        {-25, 0, -8, 8},
        {-16, 16, -15, 0}
    };

    // Enlarge hitboxes
    int ff = 3;
    int hf = 2;

    allDirs[FacingRight].Right *= ff;
    allDirs[FacingRight].Top *= hf;
    allDirs[FacingRight].Bottom *= hf;

    allDirs[FacingDown].Bottom *= ff;
    allDirs[FacingDown].Left *= hf;
    allDirs[FacingDown].Right *= hf;

    allDirs[FacingLeft].Left *= ff;
    allDirs[FacingLeft].Top *= hf;
    allDirs[FacingLeft].Bottom *= hf;

    allDirs[FacingUp].Top *= ff;
    allDirs[FacingUp].Left *= hf;
    allDirs[FacingUp].Right *= hf;

    // Transfer hitbox info into byte data
    std::vector<unsigned char> hitboxBytes;

    for (int i = 0; i < 4; ++i)
    {
        PushValue(allDirs[i].Left, &hitboxBytes);
        PushValue(allDirs[i].Right, &hitboxBytes);
        PushValue(allDirs[i].Top, &hitboxBytes);
        PushValue(allDirs[i].Bottom, &hitboxBytes);
    }

    // Patch the new tables in
    int destOffset = 0xB710;
    for (size_t i = 0; i < hitboxBytes.size(); ++i)
    {
        dataB[destOffset + i] = hitboxBytes[i];
    }

    fopen_s(&pB, "Lagoon.hitbox.v3.smc", "wb");
    fwrite(dataB.data(), 1, dataB.size(), pB);
    fclose(pB);

}

Running this patching program yields the table

Facing  	Raw data			Plain hex offsets		Signed dec offsets	
------		--------			-----------------		------------------
Right		00 00 4B 00 F0 FF 10 00		0h, 4Bh, FFF0h, 10h		0, 75, -16, 16			
Down		E0 FF 20 00 00 00 2D 00		FFE0h, 20h, 0, 2Dh		-32, 32, 0, 45	
Left		B5 FF 00 00 F0 FF 10 00		FFB5h, 0h, FFF0h, 10h		-75, 0, -16, 16			
Up		E0 FF 20 00 D3 FF 00 00		FFE0h, 20h, FFD3, 0h		-32, 32, -45, 0		

Find a convenient, buildable version of patcher here: https://github.com/clandrew/lagoonhitbox/

You can use the patcher to change the hitboxes as you want. If this concept seems useful then it’d be a good idea to fuss with the values until they yield something desirable.

Note:

  • All ROM file offsets are on headerless ROMs.
  • The hitboxes calculated from the routine described here is used for both talking to NPCs, and combat. While there might be a motive to affect only combat, there’ve also been complaints that the hitboxes when talking to NPCs are too fussy, so YMMV.
  • If you make the hitboxes obscenely large it can make the game hard to play. For example, if NPCs A and B are standing close to each other, attempting to talk to A might acidentally cause conversation with B.

This post is also available in text form here:

https://raw.githubusercontent.com/clandrew/lagoonhitbox/master/lagoon_patch_info.txt

August 27th, 2020 at 4:57 am | Comments & Trackbacks (0) | Permalink

One of my favorite retro sports games is Ice Hockey for the NES. This game gets overlooked because it’s on the simplistic side and not tied to a real-life franchise, but it’s still a good time.

I started getting into watching hockey streaming so I’ve been playing this game as something to do during intermission or when waiting for the game to start. One thing led to another and I ended up making a romhack to change the sprites over to be female looking.

Before:

After:

Some more gameplay

Here’s a demo of using the tool for simple task of crossing-out the puck sprite

Instead of crossing out the puck I made other changes to the sprites of course, and used this tool to import them back into the ROM.

Ultimately it may have been possible to use someone’s already-made tool in lieu of making a new one. I tried one, YY-CHR since it’s popular. But, I had problems getting it to understand externally-pasted or externally-imported images, and YY-CHR’s built-in image editor was not sufficient for my workflow. If that one didn’t pan out, it may not bode well for the others. Since I was familiar with the image formats it was not too much to simply make a new thing.

About this game’s mechanic, if you aren’t familiar- this is 4-on-4 hockey. Skater players come in three varieties: light, medium and heavy.

  • The light skater is fast but has a weak shot and can be knocked over easily.
  • The heavy skater is slow but has a strong shot and tends not to get knocked over.
  • And, the medium skater is in the middle.

You pick what type your 4 players should be. A typical game involves a balance of skaters, although ultimately it’s up to you.

The players, ref, goalie and zamboni driver are edited. 👍

To play it you don’t need to use the tool, of course. I’m posting a patch so you can just patch your ROM.

Click here to download the patch (IPS). Patch was created using LunarIPS. LunarIPS is also recommended for applying patches. Apply the patch to an unzipped, NA release ROM, size 40976 bytes. Don’t hesitate to contact me if you want to play but don’t know how any of this works, I’ll set you up.

And click here to download the source spritesheets if you want them for some reason.

If you want to change the sprites to fit your own creative inspiration, you too can use the tool I made, posted to GitHub here.

Update (1/15/2020): Fixed missing bun in one frame of heavy player animation, fixed back-of-ref’s-head-during-penalty animation

January 13th, 2020 at 8:25 am | Comments & Trackbacks (0) | Permalink

Animal Crossing (for Gamecube) contains a functional, hidden Famicom emulator

July 12th, 2018 at 7:58 pm | Comments & Trackbacks (0) | Permalink