6 ms·

Cramming Solitaire onto a Nintendo E-Reader card

127 points by retro_guy 2y ago

retro_guy 2y ago
Source: https://www.reddit.com/r/retrogamedev/comments/1gglfqx/cramming_solitaire_onto_a_nintendo_ereader_card/ https://www.reddit.com/r/retrogamedev/comments/1gglfqx/cramm...
davexunit 2y ago
This was a great read, the debugging substory in particular. I bought the unpopular E-Reader as a kid and felt pretty ripped off by it. If only I had known there was a z80 emulator inside. ;)
mouse_ 2y ago
impressive!
relistan 2y ago
I live deep dives like this into something obscure and cool! Looks like fun
a1o 2y ago
Does someone knows what the Mosaic E-Reader API call does? ``` RST8_26h Mosaic ;bg<n>cnt.bit6=a.bit<n>, [400004Ch]=de ```
- unleaded 2y ago
  If you search for the address 400004Ch on https://problemkaputt.de/gbatek.htm https://problemkaputt.de/gbatek.htm it leads to the mosaic control register. It does a primitive pixellation effect (no averaging or anything, it just holds the top left pixel of the region) on a background layer. The exact same effect is present in the SNES and DS and is often used for level transitions. I don't know enough Z80 to know how you use the API call though.
  - a1o 2y ago
    Thanks, I remember this transition in Super Mario World. Nice to have a name for it.
ndiddy 2y ago
Great article! I think the tiny size of the cards, the Z80 VM, and the high-ish level "scripting" API make the E-Reader a really interesting platform. I might try writing something for it if I ever get around to it.
palsecam 2y ago
> A single E-Reader dotstrip can store 2,192 bytes of data, which is just over 2kb. But there is some overhead with the headers […] data on the dotstrip is compressed though > In the end I didn't need to do too much space optimization to keep Solitaire down to two dotstrips So, a full implementation of Solitaire in ~4KiB. Count me impressed! I like to show off that my own (as a web app: https://FreeSolitaire.win https://FreeSolitaire.win) is "only" 21KiB, but that’s small fry in comparaison!
- stavros 2y ago
  > "only" 21KiB, but that’s small fry in comparaison! Or, rather, big fry.
- redundantly 2y ago
  > You finished in 6 min 32s and 118 moves. > 118 on your own + 0 hinted + 0 to auto-end. > The computer could do it in 117 moves. I've played a lot of solitaire over the past four decades, one of my favourite versions was on the HP 620LX. I'd like to think I'm just this amazing, but it feels like it was too easy. What kind of shuffling does your program use? Do you start off with easier decks to entice new users to keep playing or was it just pure chance that I got such an easy shuffle? In any regard, I like your implementation. Worked extremely well in Safari on iOS, that's an accomplishment on its own, it's rare that web based games work as well as yours did on mobile.
  - bongodongobob 2y ago
    It's easy because you're drawing one card at a time, not 3.
    - codezero 2y ago
      There’s a setting to change that :)
    - redundantly 2y ago
      It was significantly easier than other 1-card draw implementations I've played. I wonder if the logic used to ensure the game is winnable causes a bias towards easier shuffles. Still fun, though!
whamlastxmas 2y ago
Super cool, I love this!
yincrash 2y ago
Reading this, it seems like the Z80 emulator is a Gameboy emulator and the quirks that the dev was finding with the Z80 emulation was due to it not really being a Z80 emulator?
- Dwedit 2y ago
  For comparison, SMSAdvance has a proper Z80 emulator.
- JonathonW 2y ago
  Is it even an emulator? There's an SM83 (the Game Boy Color's weird not-quite-Z80 CPU) hiding inside the Game Boy Advance's SoC. [edit] Reading a bit more, it is an emulator-- and apparently an inefficient, poorly-written one at that.
  - lxgr 2y ago
    The original GBA models (including the SP) did actually feature a Sharp SM83 (the Z80-compatible CPU used in the GB and GBC) for GB/GBC backwards compatibility. It was never accessible by GBA games (or at least intended to be accessed, so to my knowledge no official titles did), and so the Game Boy Micro and the DS and DS Lite, which both feature GBA but not GB/GBC backwards compatibility, could drop it without causing any problems for GBA games.
    - Dwedit 2y ago
      GBC mode (with the z80-like processor) cannot be accessed in GBA mode at all.
    - mmaniac 2y ago
      The Game Boy Micro still contained a useable SM83 and GBC PPU on the SoC, but the cartridge is inaccessible. In theory you might be able to run a tiny payload from WRAM (32KB?) but it's pretty useless otherwise. https://github.com/AntonioND/gba-switch-to-gbc https://github.com/AntonioND/gba-switch-to-gbc
tsujamin 2y ago
I used to _love_ the E-Reader, and had a huge stack of cards for it. It was neat that it integrated into so many different games. I think my favourites were playing NES ExciteBike and the Pokemon Ruby/Sapphire/Emerald trainer cards. The E-Reader is only surpassed by the GameBoy Camera.
testplzignore 2y ago
But can it run Doom?
- egypturnash 2y ago
  A single E-Reader dotstrip can store 2,192 bytes of data, which is just over 2kb. But there is some overhead with the headers, and error correction, making the actual amount of data I've been able to store on a single strip a bit less than 2kb. This data on the dotstrip is compressed though, which helps a lot. The E-Reader itself allows a maximum of 12 strips to be scanned for a single application. You'd have to fit your Doom into about 24k, after compression. The Doom 1 demo .wad looks to be about four megabytes. That's going to be a slight problem, I hope you have some killer compression schemes. This Solitaire port is also running on a Z80. An emulated Z80. On a Gameboy Advance. With a bunch of opcodes missing. That'll be a challenge too. The Gameboy Advance that this card reader works with can run Doom, there was an official port. It looks acceptable. (https://www.youtube.com/watch?v=YzGwAKUXzvU https://www.youtube.com/watch?v=YzGwAKUXzvU) If this E-Reader can run its programs on the GBA's native hardware then you only have to implement some amazing compression schemes. Good luck beating Farbrusch's Kkreiger (https://www.pouet.net/prod.php?which=12036 https://www.pouet.net/prod.php?which=12036), that's a procedurally-generated FPS that fits in 96k...
  - ForHackernews 2y ago
    He says an eReader app can be loaded in up to 12 individual card-swipes, so you could get ~26kb. He just tried to limit himself to a single swipe.
    - gambiting 2y ago
      He limited himself to a single card not a single swipe - it still needed two swipes.
    - Uvix 2y ago
      One card, which is two swipes.
dmitrygr 2y ago
The “weird crippled z80” is the GB/C cpu which is indeed a z80 with some things removed and a few added.
- ndiddy 2y ago
  It's fairly similar, but the Gameboy CPU supports a few opcodes that the E-Reader doesn't (DAA, HALT, DI, EI) and the E-Reader has a few custom opcodes (there's a couple for waiting a specified number of frames, and a couple used for API calls). I think it's better to say that both are 8080 supersets.
Narishma 2y ago
Why do they say it's running on a Z80 emulator? Doesn't the GBA have a Z80 CPU (or rather the SM83 variant) to run GB and GBC games?
- jasonjayr 2y ago
  The ereader device has a [limited] z80 emulator.
- Uvix 2y ago
  It does have one, but it's not accessible when running in GBA mode.
- lxgr 2y ago
  The original GBA (and GBA SP) did, but the Game Boy Micro and DS Lite didn't. At least the latter is apparently compatible with the E-Reader.
msephton 2y ago
Love this! And love what they did with ERAPI. Do we know specifically who created that?
Dwedit 2y ago
With compression, elimination of dependencies, and the THUMB instruction set, would a version written in C have fit on a single card?
raymond_goo 2y ago
here is a nice Yukon solitaire variant, that is guaranteed solvable. https://www.solitairle.com/ https://www.solitairle.com/
mmmlinux 2y ago
Really wish i knew where my E-Reader wondered off to years ago. maybe one day it will show up again. I think about it time to time and wondered about the programming challenges it must have had.
fennecbutt 2y ago
If you think this is cool, then check out this guy that made additional dlc for some of the pokemon games that had new items and events distributed by dot card: https://youtu.be/fgX36SAeTwQ?si=p5YXONlbbAHW1mLe https://youtu.be/fgX36SAeTwQ?si=p5YXONlbbAHW1mLe https://youtu.be/6j4CfGlHFI8?si=Bento62buP6g974z https://youtu.be/6j4CfGlHFI8?si=Bento62buP6g974z It's pretty cool as he covers using the internal api that the pokemon games implement to handle the dot card data as well.

127 points by retro_guy 2y ago

Source: https://www.reddit.com/r/retrogamedev/comments/1gglfqx/cramming_solitaire_onto_a_nintendo_ereader_card/ https://www.reddit.com/r/retrogamedev/comments/1gglfqx/cramm...

davexunit 2y ago

This was a great read, the debugging substory in particular. I bought the unpopular E-Reader as a kid and felt pretty ripped off by it. If only I had known there was a z80 emulator inside. ;)

mouse_ 2y ago

impressive!

relistan 2y ago

I live deep dives like this into something obscure and cool! Looks like fun

a1o 2y ago

Does someone knows what the Mosaic E-Reader API call does? ``` RST8_26h Mosaic ;bg<n>cnt.bit6=a.bit<n>, [400004Ch]=de ```

unleaded 2y ago
If you search for the address 400004Ch on https://problemkaputt.de/gbatek.htm https://problemkaputt.de/gbatek.htm it leads to the mosaic control register. It does a primitive pixellation effect (no averaging or anything, it just holds the top left pixel of the region) on a background layer. The exact same effect is present in the SNES and DS and is often used for level transitions. I don't know enough Z80 to know how you use the API call though.
- a1o 2y ago
  Thanks, I remember this transition in Super Mario World. Nice to have a name for it.

ndiddy 2y ago

Great article! I think the tiny size of the cards, the Z80 VM, and the high-ish level "scripting" API make the E-Reader a really interesting platform. I might try writing something for it if I ever get around to it.

palsecam 2y ago

> A single E-Reader dotstrip can store 2,192 bytes of data, which is just over 2kb. But there is some overhead with the headers […] data on the dotstrip is compressed though > In the end I didn't need to do too much space optimization to keep Solitaire down to two dotstrips So, a full implementation of Solitaire in ~4KiB. Count me impressed! I like to show off that my own (as a web app: https://FreeSolitaire.win https://FreeSolitaire.win) is "only" 21KiB, but that’s small fry in comparaison!

stavros 2y ago
> "only" 21KiB, but that’s small fry in comparaison! Or, rather, big fry.
redundantly 2y ago
> You finished in 6 min 32s and 118 moves. > 118 on your own + 0 hinted + 0 to auto-end. > The computer could do it in 117 moves. I've played a lot of solitaire over the past four decades, one of my favourite versions was on the HP 620LX. I'd like to think I'm just this amazing, but it feels like it was too easy. What kind of shuffling does your program use? Do you start off with easier decks to entice new users to keep playing or was it just pure chance that I got such an easy shuffle? In any regard, I like your implementation. Worked extremely well in Safari on iOS, that's an accomplishment on its own, it's rare that web based games work as well as yours did on mobile.
- bongodongobob 2y ago
  It's easy because you're drawing one card at a time, not 3.
  - codezero 2y ago
    There’s a setting to change that :)
  - redundantly 2y ago
    It was significantly easier than other 1-card draw implementations I've played. I wonder if the logic used to ensure the game is winnable causes a bias towards easier shuffles. Still fun, though!

whamlastxmas 2y ago

Super cool, I love this!

yincrash 2y ago

Reading this, it seems like the Z80 emulator is a Gameboy emulator and the quirks that the dev was finding with the Z80 emulation was due to it not really being a Z80 emulator?

Dwedit 2y ago
For comparison, SMSAdvance has a proper Z80 emulator.
JonathonW 2y ago
Is it even an emulator? There's an SM83 (the Game Boy Color's weird not-quite-Z80 CPU) hiding inside the Game Boy Advance's SoC. [edit] Reading a bit more, it is an emulator-- and apparently an inefficient, poorly-written one at that.
- lxgr 2y ago
  The original GBA models (including the SP) did actually feature a Sharp SM83 (the Z80-compatible CPU used in the GB and GBC) for GB/GBC backwards compatibility. It was never accessible by GBA games (or at least intended to be accessed, so to my knowledge no official titles did), and so the Game Boy Micro and the DS and DS Lite, which both feature GBA but not GB/GBC backwards compatibility, could drop it without causing any problems for GBA games.
  - Dwedit 2y ago
    GBC mode (with the z80-like processor) cannot be accessed in GBA mode at all.
  - mmaniac 2y ago
    The Game Boy Micro still contained a useable SM83 and GBC PPU on the SoC, but the cartridge is inaccessible. In theory you might be able to run a tiny payload from WRAM (32KB?) but it's pretty useless otherwise. https://github.com/AntonioND/gba-switch-to-gbc https://github.com/AntonioND/gba-switch-to-gbc

tsujamin 2y ago

I used to _love_ the E-Reader, and had a huge stack of cards for it. It was neat that it integrated into so many different games. I think my favourites were playing NES ExciteBike and the Pokemon Ruby/Sapphire/Emerald trainer cards. The E-Reader is only surpassed by the GameBoy Camera.

testplzignore 2y ago

But can it run Doom?

egypturnash 2y ago
A single E-Reader dotstrip can store 2,192 bytes of data, which is just over 2kb. But there is some overhead with the headers, and error correction, making the actual amount of data I've been able to store on a single strip a bit less than 2kb. This data on the dotstrip is compressed though, which helps a lot. The E-Reader itself allows a maximum of 12 strips to be scanned for a single application. You'd have to fit your Doom into about 24k, after compression. The Doom 1 demo .wad looks to be about four megabytes. That's going to be a slight problem, I hope you have some killer compression schemes. This Solitaire port is also running on a Z80. An emulated Z80. On a Gameboy Advance. With a bunch of opcodes missing. That'll be a challenge too. The Gameboy Advance that this card reader works with can run Doom, there was an official port. It looks acceptable. (https://www.youtube.com/watch?v=YzGwAKUXzvU https://www.youtube.com/watch?v=YzGwAKUXzvU) If this E-Reader can run its programs on the GBA's native hardware then you only have to implement some amazing compression schemes. Good luck beating Farbrusch's Kkreiger (https://www.pouet.net/prod.php?which=12036 https://www.pouet.net/prod.php?which=12036), that's a procedurally-generated FPS that fits in 96k...
- ForHackernews 2y ago
  He says an eReader app can be loaded in up to 12 individual card-swipes, so you could get ~26kb. He just tried to limit himself to a single swipe.
  - gambiting 2y ago
    He limited himself to a single card not a single swipe - it still needed two swipes.
  - Uvix 2y ago
    One card, which is two swipes.

dmitrygr 2y ago

The “weird crippled z80” is the GB/C cpu which is indeed a z80 with some things removed and a few added.

ndiddy 2y ago
It's fairly similar, but the Gameboy CPU supports a few opcodes that the E-Reader doesn't (DAA, HALT, DI, EI) and the E-Reader has a few custom opcodes (there's a couple for waiting a specified number of frames, and a couple used for API calls). I think it's better to say that both are 8080 supersets.

Narishma 2y ago

Why do they say it's running on a Z80 emulator? Doesn't the GBA have a Z80 CPU (or rather the SM83 variant) to run GB and GBC games?

jasonjayr 2y ago
The ereader device has a [limited] z80 emulator.
Uvix 2y ago
It does have one, but it's not accessible when running in GBA mode.
lxgr 2y ago
The original GBA (and GBA SP) did, but the Game Boy Micro and DS Lite didn't. At least the latter is apparently compatible with the E-Reader.

msephton 2y ago

Love this! And love what they did with ERAPI. Do we know specifically who created that?

Dwedit 2y ago

With compression, elimination of dependencies, and the THUMB instruction set, would a version written in C have fit on a single card?

raymond_goo 2y ago

here is a nice Yukon solitaire variant, that is guaranteed solvable. https://www.solitairle.com/ https://www.solitairle.com/

mmmlinux 2y ago

Really wish i knew where my E-Reader wondered off to years ago. maybe one day it will show up again. I think about it time to time and wondered about the programming challenges it must have had.

fennecbutt 2y ago

If you think this is cool, then check out this guy that made additional dlc for some of the pokemon games that had new items and events distributed by dot card: https://youtu.be/fgX36SAeTwQ?si=p5YXONlbbAHW1mLe https://youtu.be/fgX36SAeTwQ?si=p5YXONlbbAHW1mLe https://youtu.be/6j4CfGlHFI8?si=Bento62buP6g974z https://youtu.be/6j4CfGlHFI8?si=Bento62buP6g974z It's pretty cool as he covers using the internal api that the pokemon games implement to handle the dot card data as well.