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Retro Boy: simple Game Boy emulator written in Rust, can be played on the web

338 points by ingve 2 months ago | 107 comments

zeta0134 2 months ago

This is awesome! Very nicely done. I hear a few problems with the audio emulation, (mostly clicks that shouldn't be there) but it's been a long while since I had my head wrapped around Gameboy emulation. I'm not sure I know what's going wrong exactly.

I love how Rust+WASM is an enabler for showing off applications like this which would traditionally be restricted to a desktop environment. Here's my own, an NES emulator, using wasm-bindgen for the translation but otherwise a similar setup:

https://rustico.reploid.cafe/?cartridge=patreon/tactus-v0.7-...

It's so cool to work on a bit of homebrew, then be able to share a link with someone and have it "just work" in their browser. No weird tools, no shady sites, just my game and their feedback.

diggan 2 months ago

> I hear a few problems with the audio emulation, (mostly clicks that shouldn't be there)

Almost anything WASM+Audio seems to do that in browsers today, unless you're really really careful about what you're doing and leverage multiple threads. I think the issue is mostly around single-thread contexts, where it has to switch between playing audio and other things.

I hit the very same issue myself with Bevy not too long time ago, and tracking this issue which has some further links if you wanna go down a rabbit-hole: https://github.com/bevyengine/bevy/issues/4078

samiv 2 months ago

I've had the same issue in my engine.

What I've found is that essentially WebAudio has such a terrible performance that the audio buffers need to be at minimum 100ms. And if you have a bad frame or any jank in your RAF is likely to glitch at least occasionally.

Compare this to when running natively 20ms audio buffers are fine.

I've settled on a design where I run all the audio graphs and audio decoding in a separate thread and then queue the audio buffers for the main JS thread to pick up and make the WebAudio calls. The same has to be done for the graphics (WebGL) as well. This can be major paradigm shift if the initial design has been done around doing stuff independently on the background. On the web.. no can do.

Bonus tip, if you're planning to use the OpenAL implementation that Emscripten provides my only advice is.. don't.

2c2c2c 2 months ago

i combed through quite a few hobbyist gb emulators while writing mine and found audio to be pretty rarely finished or finished without issues. not sure if it's the same for NES

zeta0134 2 months ago

Audio is *surprisingly* tricky on both platforms. NES has DPCM, which cheerfully interrupts the CPU and causes untold issues with controller reading. Gameboy has envelopes that are semi-required with phase-resets, and a wave channel which you in theory cannot write new samples to, and developer hacks to work around both. Both systems have various hardware revisions that have subtly different behavior, and a handful of games that will break on that specific model. It's fun!

gblargg 2 months ago

It's also more involved to verify operation. Graphics are easier to "measure" and compare. Sound is also much more timing-dependent, e.g. when timers are running on their own all the time. It's disconcerting when sound is slightly off in games.

jvanderbot 2 months ago

Enthusiast noob question. What do you use for display / rendering / gui when doing emulators for wasm?

zxvkhkxvdvbdxz 2 months ago

Wasm executes as its own VM, so you'll need some js glue to display something in the browser.

This means you can go both ways, either embed something like imgui in your wasm, or build a ui using html.

darknavi 2 months ago

Or go full circle and use something like GameFace to render react in your app, in the browser!

maybeOneDay 2 months ago

Tangentially related - I recently picked up a retro gaming handheld from Aliexpress for the meagre sum of £50, which is capable of playing consoles from gameboy to snes to playstation 1, and apparently even a smattering of N64 and dreamcast (with poor performance).

There are a dizzying array of options (game boy form factor, horizontal, clamshell design ala the advance SP), and although I'm sure the build quality leaves a lot to be desired, for my personal circumstances of "I'm travelling a lot but can't quite justify a steam deck right now" it has truly been an utter delight. There's a scene of various custom firmwares to install, and apps for these firmwares to add various functionality.

I'd encourage anyone who feels a desire to play some emulated games check out /r/SBCGaming to see what's out there!

Just don't ignore the warnings that these devices don't negotiate USB C charging correctly, and also buy yourself a very small weak charger...

fernandotakai 2 months ago

if people want more info on these devices, russ from retro game corps does a ton of reviews on them, from the cheapest (that are less than 30 euro) to the really expensive ones (600+!).

i myself own a retroid pocket 5, one trimui brick (which my wife adores) and a steam deck (yes, it's an amazing retro gaming machine).

(retro catalog also has a ton of technical information, including ratings)

https://www.youtube.com/@RetroGameCorps

https://retrogamecorps.com/

https://retrocatalog.com/

tracker1 2 months ago

Thanks for the share... been using a Beelink SER8 for about 6 months or so with Chimera, which has been mostly okay... I have to reset audio out to hdmi each boot and a couple other niggles with the Bluetooth controllers. May need to switch to ones that use custom/proprietary USB dongles with lower latency.

jcjmcclean 2 months ago

Hi there! I'm running the exact same setup and have encountered the same issues.

I have a little bash script [1] which I run on startup to fix the HDMI audio issue. I haven't got crontab working yet so I ssh in and run it manually.

I've tried 3 different controllers and ended up buying the 8bitDo ultimate as it supports 2.4g as well as Bluetooth. Also purchased a separate Bluetooth dongle and a usb extension cable to keep it away from any interference from the Beelink. Still have major issues with connectivity over a reasonably short distance (3-4m) in either mode.

Love the SER8 though, it's a great little machine and is well priced when on offer.

[1] https://gist.github.com/jcjmcclean/a59362a01a7f421e4fa020823...

tracker1 2 months ago

Had been looking at a one of the same controllers, using two over 2.4g with their dongle(s). May reset the whole thing when I do... have had trouble with the second connected controller always being controller 1, that I can't seem to fix.

drakythe 2 months ago

+1 for Retro Game Corps, not only are his videos well made and informative he puts together guides for everything from basic retroarch configuration to how to install alternative OSes for specific devices (and why you might want to do that).

criddell 2 months ago

I bought an Analogue Pocket which sounds similar to what you have and I've found the games... underwhelming. I've tried a lot of games (the internet archive has them for some reason) and the only ones I've wanted to play more than once is the original Tetris and a game I don't remember the name of but it has numbers at the top and sides which you use to deduce which cells are on and eventually you reveal a pixel image.

I never had one of these devices while they were current which makes me wonder if the key ingredient to enjoying one is nostalgia?

I also have a Sony PSP (bought around 2010) which is a great bit of hardware, but I have yet to find a game that appeals to me.

tracker1 2 months ago

I've had the best luck with the Argon USB C power supplies for RaspberryPi 3/4 connected to USB/SATA adapters with SSDs. Most other power supplies I've tried get low power warnings constantly. The inline power switch is cool to, though less useful with the cases I've used.

Keyframe 2 months ago

Miyoo Mini Plus. It's fantastic!

maybeOneDay 2 months ago

Nice! I went for the Anbernic 40xxH and it's a joy to use. The only thing I wish worked differently was Retro Achievements working offline!

smparsons 2 months ago

Hi guys, original creator of the emulator here. I am shocked by how much attention my little hobby project is getting. Thanks for the support.

yoyohello13 2 months ago

Thanks for posting this! Your repo is very nicely organized.

I've been wanting to get in to making an emulator (chip8). I decided early I wanted it to run on wasm, but have been stuck in the weeds of what framework/tools to use to actually get it done. I've looked into game engines and egui, but they just add so much extra complexity.

I think seeing your repo I'm just going to try the straight wasm-bindgen + canvas route. So thanks again for making this.

smparsons 2 months ago

Actually I didn't post this on HackerNews. Somebody else did. But I'm glad to hear you got inspiration from my emulator. Yeah I found wasm-bindgen pretty easy to use.

rollcat 2 months ago

I feel like the GB/GBC/GBA are pretty much what the VT102 is to writing grid-cell software. The demo scene keeps cranking. Chiptune is still in love with the hardware - especially with the OG DMG, with a pro sound mod. Writing new software for the GBA feels a lot like targeting a tiny, modern ARM microcontroller. The hardware is well documented and understood by the enthusiasts, and it's a stable target.

Plus there are plenty of emulators focusing on different aspects: one is focusing on perfect emulation; another will try to squeeze out performance; another might offer memory inspection and "cheat codes"; this one makes it available on the web. There's beauty in all of that.

araes 2 months ago

List of links and support documents for those interested in Gameboy Development (and example Homebrew ROMs)

Gameboy Dev: https://gbdev.io/

PanDocs (tech reference): https://gbdev.io/pandocs/

Gameboy Tech Ref Doc (gekkio): https://gekkio.fi/files/gb-docs/gbctr.pdf

Game Boy Development Kit 2020 (GBDK-2020) Reboot: https://gbdk-2020.github.io/gbdk-2020/docs/api/

GBDK-2020 Github: https://github.com/gbdk-2020/gbdk-2020

GBDK-2020 Examples: https://github.com/gbdk-2020/gbdk-2020/tree/develop/gbdk-lib...

GBDK Showcase (Homebrew Software): https://gbdk-2020.github.io/gbdk-2020-gallery/

Homebrew Hub: https://hh.gbdev.io/

Neil Young Album (Silver & Gold) with Cover Image produced using the Gameboy Camera: https://en.wikipedia.org/wiki/Silver_%26_Gold_(Neil_Young_al...

GaggiX 2 months ago

Fun fact the emulator works fine on Ladybird too, even thought it's very slow now.

noeatnosleep 2 months ago

Avid millennial gamer here. Wasn't raised with games. Can someone recommend a good classic game to try?

s369610 2 months ago

Kirby's Dream Land is pretty fun too (esp after watching https://www.youtube.com/watch?v=PBRt2D2YN44 which is where the creator talks about the concepts of the game)

bityard 2 months ago

I always played games growing up but didn't play Kirby until much later in life. Kirby is easily my favorite platformer, even ahead of Mario and Sonic. I wish there were more like it.

frosting1337 2 months ago

Pokemon - Red/Blue or Gold/Silver, and Legend of Zelda: Links Awakening.

matcha-video 2 months ago

seconded! I also enjoyed Zelda: Oracle of Ages / Seasons

aussieguy1234 2 months ago

The game boy Tetris was the first version I played, it was pretty good.

Nowdays for a mobile Tetris option i'm using a SNES emulator on my phone (Snes9x EX) and Super Tetris.

Meanwhile, there are companies creating on the web and mobile app versions of Tetris, inserting ads and charging money for what should be free.

coldpie 2 months ago

Super Mario Land is a good place to start. The music is great, and it is very short and pretty easy.

Link's Awakening is my favorite Zelda game.

The original Pokemon games (Red/Blue, Gold/Silver) that others are recommending are pretty rough these days, but it's fun to see where it all started if you have the patience for them.

If you want something a little less well-known, Bubble Ghost is a fun little puzzler.

Regardless of what you try, remember that this is the era when game manuals were required reading since they rarely were able to fit tutorials & instructions in-game. It's good to scan through the manual first before you play something or you might be missing some critical information.

gwbas1c 2 months ago

Super Mario Land, 1 and 2. Dr. Mario.

Game Boy games tended to be limited due to space constraints.

lxgr 2 months ago

There are definitely limitations, but later games have a lot more depth than these.

Link's Awakening feels like it shouldn't be possible in a single megabyte of mask ROM, for example. The fact that it was makes it almost more impressive by today's standards.

djtango 2 months ago

Games back then were a bit of a dark art...

I feel like I don't really encounter stories of heroics in making games work on their hardware anymore. Even at the end of PS1 with Final Fantasy their hand drawn backgrounds were too big to fit into VRAM iirc

Or in the PS2 era Jak and Daxter using the principle of hot reloading from lisp to figure out open worlds without loading screens

Narishma 2 months ago

The limitations nowadays for game development are more on the budget side than the hardware.

wing-_-nuts 2 months ago

The fact that a single dev used to be able to complete an entire game really makes me wish I had come of age back in the day when that was possible. I feel like you can only approach something similar with pico-8 or another fantasy console these days.

lxgr 2 months ago

But it still is! None of the technology that made these games possible has disappeared; quite the opposite, as you already mention (with Pico-8 etc.)

djtango 2 months ago

Wasn't Hollow Knight put together with a really tiny team?

RetroSpark 2 months ago

> Link's Awakening feels like it shouldn't be possible in a single megabyte of mask ROM

Half a megabyte, even! (For the original monochrome game - the later color version is a full megabyte.)

lxgr 2 months ago

Ah, right, I fortunately slept on it long enough to get the DX version right away! The photographer side plot was amazing, especially with a Game Boy Printer :)

xtracto 2 months ago

I has SML 1 and OperationC in the original game boy. Such great games. Also links awakening!!

999900000999 2 months ago

Tetris or Pokemon Red.

Pokemon is actually a really difficult game before modern QOL. No DLC!

Xenoamorphous 2 months ago

For the original GameBoy, without a doubt: Zelda Link's Awakening.

kibwen 2 months ago

But get the DX edition for the GBC.

nosrepa 2 months ago

It's always good to see usernames I recognize from the other site.

johnisgood 2 months ago

I know right. :D

MyOutfitIsVague 2 months ago

Game Boy, or any classic game?

Wario Land 3 is a really really good Game Boy Color game.

kibwen 2 months ago

For the Game Boy/Color, I recommend Wario Land II and Donkey Kong (1994) as sleeper hits.

dpedu 2 months ago

Dragon Warrior 1, 2, and 3 are all awesome official ports - they were originally for the NES.

andrepd 2 months ago

Pokémon is the quintessential Game Boy game

jaredhallen 2 months ago

Super Off Road

philips 2 months ago

Mole Mania

patrickcorrigan 2 months ago

Really love seeing more Game Boy emulators written in Rust, especially with browser support — awesome project!

If you're into this space, I’ve been building https://afterplay.io — a browser-based retro gaming platform with support for a bunch of systems (GB,GBC, GBA, SNES, NDS, PS1, etc). It runs entirely in the browser with save states, cloud sync, and native mobile support via Capacitor.

Also has some fun stuff like netplay (multiplayer over the web), Link Cable Support and RTC manipulation, and customisable touch controls.

Always exciting to see more emulators pushing what’s possible on the web.

ericzawo 2 months ago

I remember being 7 years old figuring out how to unzip the no$gbemulator to play Kirby and Final Fantasy Adventure on my dad's Windows 95 laptop. Good times.

pests 2 months ago

Same, first emulator I ever used, maybe a little after you (Windows 98)

The ability to speed up time made leveling up pokemon so much easier back in the day. Walking back and forth in the grass.

Also my first introduction to save states outside the game itself / quick loading.

shaoner 2 months ago

It's been a while since I touched it but I have a very similar GB emulator in rust:

- The library: https://github.com/shaoner/padme-core

- The web/wasm backend: https://github.com/shaoner/padme-browser

catapart 2 months ago

It plays really slow in Firefox, and there are also audio issues (they may be related?)

But in Chrome, this plays really well! Great work!

shakna 2 months ago

WebRender recently got much slower in Firefox [0].

I haven't looked at the source yet, but if the bitmaps aren't all preallocated, then it'll run into this repeatedly.

[0] https://treeherder.mozilla.org/perfherder/graphs?highlightAl...

adrian17 2 months ago

For me it runs at full speed in both stable and developer versions of Firefox (but even then, audio is bad at times). But still, I looked at performance out of curiosity.

After running it under FF's profiler for a moment, it looks like a sync executed after every opcode recalculates the framebuffer (`step_until_next_audio_buffer -> cpu::microops::read_byte_from_memory -> emulator::sync -> gpu::scanline::write_scanlines`) and uploads it to the canvas with `putImageData`, which takes ~35% of execution time. Sounds like that could be redundant work, since I'm pretty sure the canvas isn't actually redrawn until the wasm execution yields back to the browser.

EDIT: also, the emulator can't really be ran in debug mode, since 1. it blows the wasm stack (presumably when creating the huge `Emulator` struct, a not uncommon issue in Rust; I had to hack in bigger stack size with linker args), and 2. is panics on int overflows `apu::step`.

catapart 2 months ago

Yeah, still being on Windows 10, I almost didn't put the complaint in the comment. Lots of reasons it might just be an environment issue for me.

But, in my development experience with firefox, the issues it seems to have always seem performance related (or compliance with web standards related), and I figured that even if others weren't seeing the issue, there was still probably something underlying that could be figured out. So thanks for going through the debug! It's nice to know that there may be an optimization available for the project, and it feels like it might even be an additional performance gain for chromium, if I'm understanding you right? Might be some reason they need to do that sync after every opcode, but I agree with your suspicion that the canvas is probably being over-rendered to.

adrian17 2 months ago

FWIW, the thing I've found as the slowest single factor on my machine, might not be the slowest on yours; I might have not noticed the real cause of slowdowns on your machine at all, and you may be the only one able to diagnose it.

(and for the record, I'm on W10 too.)

Also, my personal experience from optimizing https://ruffle.rs/ is that in many cases Firefox's wasm runtime can behave slightly faster than on Chrome for some reason; and performance issues are often instead caused by other APIs like the canvas.

tonyhart7 2 months ago

ofc it is firefox

ShinTakuya 2 months ago

Can I inquire as to why you feel so negatively about Firefox?

tonyhart7 2 months ago

burn a lot of fcking goodwill for measly 4% web user, turn out eating google money literally make you the next "google"

chromium edge literally surpass firefox and with new policy it would eat more to the marketshare

ShinTakuya 2 months ago

Is it that surprising that Edge is surpassing Firefox given Firefox doesn't have the onboarding ramp of Microsoft and Google? Microsoft shoves Edge in your face every chance it gets, as does Google. What can Mozilla do to compete against that? Unfair to use market share as an argument.

tonyhart7 2 months ago

"What can Mozilla do to compete against that?"

well if only Modzilla foundation spend money given to them to actual firefox development instead of ehm ehm DEI policy (lol) and pay executive millions of dollars

at this rate even brave,opera browser would surpass firefox

ShinTakuya 2 months ago

While I agree they shouldn't be putting their money towards political causes, the scrutiny of the budget is also political in nature. Of the $400 million in expenses, only around $15 million went to executives, and around $1 million went to the DEI stuff. The rest was split evenly between developing and marketing Firefox, which is basically what you were criticising them on not doing.

If they got rid of all the executives and DEI, they could increase the other budgets by 2%. There is 0 chance that the 2% extra budget could help the market share and development in any significant way.

And if you don't pay executives enough, you get worse executives who make worse decisions because the good ones will go to other companies. So you'll be complaining even more if the $15 million executive pay got dropped.

So in short: I agree Mozilla shouldn't get involved in politics. Despite this, no reasonable person could look at the numbers and conclude it's having a material effect on the destiny of Firefox.

tonyhart7 2 months ago

ok my past response is mostly for laugh, this is my serious response

Firefox is literally default install in most if not all linux distro os, while I agree that situation is far from ideal but nothing is can be blamed other than themselves

for the longest of time firefox always playing catch up with chromium to achieve parity, maybe just maybe we don't need more browser

Microsoft literally give up their browser (IE), given how much resource MS has do you think firefox is doomed?? especially with DOJ force google to breakup chrome and cut off their spending on modzilla

I mostly critize about firefox place in the market, Opera found an niche with Opera GX for gaming, Brave with adblock and privacy focused etc while firefox is what??? inferior of chrome???

ShinTakuya 2 months ago

I can't reply further to this thread without this devolving into a flame war so I'll just observe that you've moved the goal posts claiming you were just joking, and refuse to engage further until you acknowledge you're either getting defensive for no reason or arguing in bad faith.

tonyhart7 2 months ago

Yeah because you didn't have argument for it, good try tho

it would work with other people but not for me

edit: I'm not joking, I said laughing because firefox state is pathetic that deserved to be laughed at

d3k 2 months ago

Nice! it reminds me of a very similar project a friend of mine did like 10 years ago https://github.com/simias/gb-rs

wjholden 2 months ago

This is the first time that I've noticed a website where I can add the page as an Android app. What is this called and how can I get started making my own web applications into installable apps?

myscreant 2 months ago

I do this all the time. It's a PWA (progressive web app). To make your own, you need to add a manifest.json at the root.

Additionally, on Android, there are apps like Hermit / NativeAlpha that will create a wrapper around any site.

mytailorisrich 2 months ago

Note his personal blog for some more info on the development: https://samthecoder.com/

turnsout 2 months ago

Looks like an awesome addition to the GB emulation world! I know GB Studio can export a web player—I wonder if this implementation has some advantages.

cglong 2 months ago

One major disadvantage is that this one doesn't seem to have an OSS license :(

mbrubeck 2 months ago

Looks like the author has fixed that; it’s now available under the Apache License 2.0.

chrismaltby 2 months ago

I’ll definitely have a look and see if there’s any advantages. Currently using binjgb in GB Studio and been pretty happy with it https://github.com/binji/binjgb

ajsnigrutin 2 months ago

Why does almost every project written in rust have "written in rust" advertised in the title/description?

jamienicol 2 months ago

Because people are interested in how technology is built, and if they’re interested in rust they might be interested in seeing how it’s used in other projects

dvhh 2 months ago

sure that "being written in C" or in "PHP" would have gathered far less interest

llarsson 2 months ago

A GameBoy emulator written in PHP would certainly piqued my interest, but more like a morbid curiosity than anything else. :)

tonyhart7 2 months ago

because rust is screaming bleeding edge

sydon 2 months ago

This is very cool. Whenever I see a project like this I wonder "how did they even get started".

SaintRomuald 2 months ago

A gameboy emulator is a very popular project. There are plenty of guides on how to get started. Checkout "build your own x" repo for some project ideas

yakkomajuri 2 months ago

Got right to playing Donkey Kong Country! Thanks for this, really cool.

GaggiX 2 months ago

Given the topic, does anyone has some cool homebrew ROM for the gameboy?

hananova 2 months ago

I have written my own game for the original game boy[1] with the goal of bringing very modern tetris (Think Tetris the Grand Master) to a retro system. It's free and open source. Though the sound seems to not work well on the emulator in parent. I've tested it on real hardware and it is definitely an emulator bug.

1. https://github.com/Villadelfia/dmgtris

lxgr 2 months ago

Opossum Country is pretty neat: https://benjelter.itch.io/opossum-country

dylan604 2 months ago

I see these retro emulators pop up from time to time, but I just don't have the time to really check them out (or the discipline to realize always an addict looking to avoid relapse). I know that there are "complications" about the ROMs to use in the emulator. However, is there a scene of people making ROMs of new games specifically for playing in these emulators? Are the game devs that are making modern games for retro systems that would be free of the "complications"?

small_scombrus 2 months ago

People are making new GameBoy games[0]! Even new carts[1]!

Though I imagine the rise of systems like the Pico8 and tic80 are siphoning people away because they can be run anywhere.

0 - https://archive.org/details/grimaces-birthday

1 - https://orangegb.com/orangefm/

lochnessduck 2 months ago

Then there’s chip8 and a chip8 emulator on the gameboy :) https://github.com/lancekindle/damaged-chip8

lxgr 2 months ago

Then again, a Game Boy emulator is usually the second thing people port to any given platform (immediately after Doom) :)

girvo 2 months ago

And all of the ones ModRetro is publishing!

https://modretro.com/collections/games

planetafro 2 months ago

Have you seen the pico8 software?

https://www.lexaloffle.com/pico-8.php

dylan604 2 months ago

I have now!

philips 2 months ago

Random list here I made: https://itch.io/c/2058440/gameboy

alexpadula 2 months ago

Flippin awesome. Can't wait to dive in :D

joaomoreno 2 months ago

What a clean repo, great job!

codecarter 2 months ago

This is sick. Nicely done

ferristhecrab 2 months ago

This is awesome

Thaxll 2 months ago

There are millions of emulator for the GB it's like a week-end project, what's different here?

hananova 2 months ago

A GB emulator is definitely not a weekend project if your goal is any kind of accuracy. And even if it was, that doesn't devalue the project or effort that went into it.

throwee2000 2 months ago

As someone who appreciates emulator development projects, I'd like to offer some perspective:

Several aspects make every new GB emulator implementation valuable to the community.

Some technical challenges in emulation are approached differently by each developer.

Handling edge cases and accuracy testing requires significant effort beyond basic functionality.

Often the learning process and personal growth are the primary goals, not just the end product.

Languages like Rust bring modern benefits like memory safety and performance to classic emulation.

Emulator development teaches low-level hardware concepts in an engaging, practical way.