8 ms·

Zelda: Link's Awakening game engine documentation (2021)

335 points by adamdegas 4y ago

fabiensanglard 4y ago
The art of living within a Vblank. Really cool read :) ! I assume A Link to the Past engine worked a lot like that too.
MBCook 4y ago
This was a great read. I’ve been writing a Game Boy emulator for fun recently and this really helps explain how developers “put the parts together” to handle some of the hardware limitations and get such a great and complex (relative to early games) result. Does anyone know of breakdowns like this for other GB games, or at least parts of them? Note the article contains links to two more specific blog posts on how the rendering loop works and how the game manages playfield tile sets to avoid corrupted graphics. Both are great reads too, don’t miss ‘em.
- pizza234 4y ago
  > Does anyone know of breakdowns like this for other GB games, or at least parts of them? I don't know any, but you may enjoy "I am error", a very technical book about the Nintendo (NES) console and its software. It also included a (again, technical) 45+ pages chapter mainly focused on Mario.
- deleted 4y ago
  [deleted]
deafpolygon 4y ago
This was a fascinating read. I hope the documentation will get filled out some more over time.
samch93 4y ago
Link's Awakening is such a weird but fascinating entry in the Zelda series. I was not surprised to learn that its story was directly influenced by Twin Peaks.
- manojlds 4y ago
  My fav Zelda to date.
- dm319 4y ago
  Tell me more! EDIT: Ok it was easy to google. TIL.
  - samch93 4y ago
    The Gaming Historian has a good video about the development of the game (https://youtu.be/pfvk6CJ3v34 https://youtu.be/pfvk6CJ3v34)
- sprkwd 4y ago
  I love this.
aliswe 4y ago
I like the ratio - many liked it, not many had much to say.
- deleted 4y ago
  [deleted]
kemenaran 4y ago
Author here! Most of the engine documentation was figured out by many romhackers over the years; I merely started the efforts to write a comprehensive overview. If you're interested in projects taking advantage of this knowledge, the Daid's LADX Randomizer [0] is awesome. It includes a ton of assembly tweaks that makes the engine more flexible, and add many options to the game. And Link’s Awakening Redux [1] is a good example of life-improvement game tweaks made using the disassembly. [0] LADXR: https://daid.github.io/LADXR/ https://daid.github.io/LADXR/ [1] Link’s Awakening Redux: https://github.com/ShadowOne333/Links-Awakening-Redux https://github.com/ShadowOne333/Links-Awakening-Redux
- wodenokoto 4y ago
  What was censored and what was the untranslated present?
  - LukeShu 4y ago
    Instead of losing her bikini top (which Link must then find), the mermaid loses her necklace. Instead of pulling a towel to cover herself when Link enters the room, the hippo lady being painted is edited to have no nude characteristics.
    - coldpie 4y ago
      Lots more here: https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Game_Boy) https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Ga... Especially on the version differences sub-page: https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Game_Boy)/Version_Differences https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Ga...
- a_t48 4y ago
  I've been working on a project on top of LADXR, many thanks to all involved.
- causality0 4y ago
  Nice. I wonder if they'd be willing to fix the bug where pressing left and right on the d-pad at the same time renders Link's sprite invisible. Not an issue on original hardware but quite dangerous when emulating.
t0bia_s 4y ago
Link's Awakening was my favorite GB game together with Pokémon Blue. What a memories! It's awesome to have those documentation so many years later.
pierreyoda 4y ago
Very cool article! If you want to know more about the hardware side of the Game Boy (Color), have a look at the Pan Docs: https://gbdev.io/pandocs/ https://gbdev.io/pandocs/ It's been revamped in the recent years, in terms of presentation. I do kind of miss the old version which had a refreshing "old-school" UI like the RFCs of the IETF, but the newest version is IMHO much more usable when developing an emulator.
nyanpasu64 4y ago
> Which means that by design, a “Keep current” section can only use the tiles shared by the adjacent tilesets, in that case the Tilesets A and B. If this rule is not honored, the graphics of the “Keep current” section will be corrupted. Semi-related, in LTTP, is this related to the corrupted graphics after performing Death Mountain Descent (performing a glitched room transition between two normally disjoint areas of the dark world map)?
- jsmith45 4y ago
  Kind-of. The basic idea of needing to be able to display both screens with the same tileset during screen transitions does exist. The game has a common section, and a section that can vary by screen. However most screens just use the common section, with only some screens using the unique section. Between any two unique sections the game will have at least one screen that does not use that section of the tilemap. On screen transition, if the transitioned to screen needs a unique section, it is loaded, and then the screen starts to scroll. However the game will correctly handle going directly from one screen that uses the unique section to another. The only issue is that the old screen may look weird between when the new section is loaded, and scrolling has finished. So what is happening with death mountain ascent/descent? Well, the death mountain area actually uses a modified version of the global tileset. (And modified versions of certain global palette entries). Normally it is not possible to go from the rest of the overworld to death mountain or vice versa, except via a cave (and switching from underworld to overworld requires reloading the tilesets), or via flute (where the same occurs). The game lacks any code to modify the global part of the overworld tileset (and palettes) on a normal screen scroll transition, as that is never supposed to be needed in normal gameplay. (There are similar considerations about what enemies can appear on adjacent screens, due to needing to manage sprite tilesets.)
mastersummoner 4y ago
Just chiming in - my absolute favorite GB game growing up. Fantastic storyline, amazing music, fun secrets. One of the best ever made for the system without a doubt.
MAGZine 4y ago
This is some really nice documentation, and in one spot rather than strewn about. Major props for consolidating the information here! In contrast, Ocarina of Time has been thoroughly torn apart, but the documentation isn't centralized anywhere. A lot of it has ended up in pastebins and shared through discord servers. I do worry that a lot of the knowledge will be lost once reversing the game is less in-vogue. An example of this is that someone read through the assembly of how the fishing minigame works, which has many dependent variables. Various factors affect how quickly you can catch a fish, and which size you will catch. Speedrunners have abused this information to make the fishing minigame as 'easy' as possible despite it being based on random chance. It's a really fascinating read[0][1]... too bad it will eventually be lost to the sands of time. [0] https://pastebin.com/WQrpxRCM https://pastebin.com/WQrpxRCM [1] https://pastebin.com/tsWjERR5 https://pastebin.com/tsWjERR5
pipeline_peak 4y ago
I used to wonder if the old game boy Zelda’s and Pokémon shared any code, my guess is probably not. On that topic, Metroid Fusion supposedly uses the Warrior Land 4 engine https://youtu.be/1ZyD9Z3jYfA https://youtu.be/1ZyD9Z3jYfA
deleted 4y ago
[deleted]

335 points by adamdegas 4y ago

The art of living within a Vblank. Really cool read :) ! I assume A Link to the Past engine worked a lot like that too.

This was a great read. I’ve been writing a Game Boy emulator for fun recently and this really helps explain how developers “put the parts together” to handle some of the hardware limitations and get such a great and complex (relative to early games) result. Does anyone know of breakdowns like this for other GB games, or at least parts of them? Note the article contains links to two more specific blog posts on how the rendering loop works and how the game manages playfield tile sets to avoid corrupted graphics. Both are great reads too, don’t miss ‘em.

pizza234 4y ago
> Does anyone know of breakdowns like this for other GB games, or at least parts of them? I don't know any, but you may enjoy "I am error", a very technical book about the Nintendo (NES) console and its software. It also included a (again, technical) 45+ pages chapter mainly focused on Mario.
deleted 4y ago
[deleted]

deafpolygon 4y ago

This was a fascinating read. I hope the documentation will get filled out some more over time.

samch93 4y ago

Link's Awakening is such a weird but fascinating entry in the Zelda series. I was not surprised to learn that its story was directly influenced by Twin Peaks.

manojlds 4y ago
My fav Zelda to date.
dm319 4y ago
Tell me more! EDIT: Ok it was easy to google. TIL.
- samch93 4y ago
  The Gaming Historian has a good video about the development of the game (https://youtu.be/pfvk6CJ3v34 https://youtu.be/pfvk6CJ3v34)
sprkwd 4y ago
I love this.

aliswe 4y ago

I like the ratio - many liked it, not many had much to say.

deleted 4y ago
[deleted]

kemenaran 4y ago

Author here! Most of the engine documentation was figured out by many romhackers over the years; I merely started the efforts to write a comprehensive overview. If you're interested in projects taking advantage of this knowledge, the Daid's LADX Randomizer [0] is awesome. It includes a ton of assembly tweaks that makes the engine more flexible, and add many options to the game. And Link’s Awakening Redux [1] is a good example of life-improvement game tweaks made using the disassembly. [0] LADXR: https://daid.github.io/LADXR/ https://daid.github.io/LADXR/ [1] Link’s Awakening Redux: https://github.com/ShadowOne333/Links-Awakening-Redux https://github.com/ShadowOne333/Links-Awakening-Redux

wodenokoto 4y ago
What was censored and what was the untranslated present?
- LukeShu 4y ago
  Instead of losing her bikini top (which Link must then find), the mermaid loses her necklace. Instead of pulling a towel to cover herself when Link enters the room, the hippo lady being painted is edited to have no nude characteristics.
  - coldpie 4y ago
    Lots more here: https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Game_Boy) https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Ga... Especially on the version differences sub-page: https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Game_Boy)/Version_Differences https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening_(Ga...
a_t48 4y ago
I've been working on a project on top of LADXR, many thanks to all involved.
causality0 4y ago
Nice. I wonder if they'd be willing to fix the bug where pressing left and right on the d-pad at the same time renders Link's sprite invisible. Not an issue on original hardware but quite dangerous when emulating.

t0bia_s 4y ago

Link's Awakening was my favorite GB game together with Pokémon Blue. What a memories! It's awesome to have those documentation so many years later.

pierreyoda 4y ago

Very cool article! If you want to know more about the hardware side of the Game Boy (Color), have a look at the Pan Docs: https://gbdev.io/pandocs/ https://gbdev.io/pandocs/ It's been revamped in the recent years, in terms of presentation. I do kind of miss the old version which had a refreshing "old-school" UI like the RFCs of the IETF, but the newest version is IMHO much more usable when developing an emulator.

nyanpasu64 4y ago

> Which means that by design, a “Keep current” section can only use the tiles shared by the adjacent tilesets, in that case the Tilesets A and B. If this rule is not honored, the graphics of the “Keep current” section will be corrupted. Semi-related, in LTTP, is this related to the corrupted graphics after performing Death Mountain Descent (performing a glitched room transition between two normally disjoint areas of the dark world map)?

jsmith45 4y ago
Kind-of. The basic idea of needing to be able to display both screens with the same tileset during screen transitions does exist. The game has a common section, and a section that can vary by screen. However most screens just use the common section, with only some screens using the unique section. Between any two unique sections the game will have at least one screen that does not use that section of the tilemap. On screen transition, if the transitioned to screen needs a unique section, it is loaded, and then the screen starts to scroll. However the game will correctly handle going directly from one screen that uses the unique section to another. The only issue is that the old screen may look weird between when the new section is loaded, and scrolling has finished. So what is happening with death mountain ascent/descent? Well, the death mountain area actually uses a modified version of the global tileset. (And modified versions of certain global palette entries). Normally it is not possible to go from the rest of the overworld to death mountain or vice versa, except via a cave (and switching from underworld to overworld requires reloading the tilesets), or via flute (where the same occurs). The game lacks any code to modify the global part of the overworld tileset (and palettes) on a normal screen scroll transition, as that is never supposed to be needed in normal gameplay. (There are similar considerations about what enemies can appear on adjacent screens, due to needing to manage sprite tilesets.)

mastersummoner 4y ago

Just chiming in - my absolute favorite GB game growing up. Fantastic storyline, amazing music, fun secrets. One of the best ever made for the system without a doubt.

MAGZine 4y ago

This is some really nice documentation, and in one spot rather than strewn about. Major props for consolidating the information here! In contrast, Ocarina of Time has been thoroughly torn apart, but the documentation isn't centralized anywhere. A lot of it has ended up in pastebins and shared through discord servers. I do worry that a lot of the knowledge will be lost once reversing the game is less in-vogue. An example of this is that someone read through the assembly of how the fishing minigame works, which has many dependent variables. Various factors affect how quickly you can catch a fish, and which size you will catch. Speedrunners have abused this information to make the fishing minigame as 'easy' as possible despite it being based on random chance. It's a really fascinating read[0][1]... too bad it will eventually be lost to the sands of time. [0] https://pastebin.com/WQrpxRCM https://pastebin.com/WQrpxRCM [1] https://pastebin.com/tsWjERR5 https://pastebin.com/tsWjERR5

pipeline_peak 4y ago

I used to wonder if the old game boy Zelda’s and Pokémon shared any code, my guess is probably not. On that topic, Metroid Fusion supposedly uses the Warrior Land 4 engine https://youtu.be/1ZyD9Z3jYfA https://youtu.be/1ZyD9Z3jYfA

deleted 4y ago

[deleted]