Glad to see some progress, looks amazing!

Nice work on this! It looks like it's running quite smoothly, and I'm excited to see how the project continues to evolve. How's the file size looking currently?

455 KB. The original game's 512 KB, but I was able to get rid of 32 KB of that, since it was audio related.

I know today's an international holiday, but I just couldn't help myself from finding out what was wrong with the tilemap rendering. It turned out to mostly be because of a typo in the routine determining the mirroring direction of a tile. I'm saving drawing directly to the screen for next year, but here's the framebuffer's output:



And here's what it looked like before I fixed it:



The frame is rendered in the Master System's 256x192 resolution, and then copied to the screen scanline-by-scanline. This is because doing it that way saves two dozen KB of RAM, and also because it allows for the easiest method of emulating tilemap scrolling.

Also, see that big mess to the right of Tails? That's not a bug in the renderer. I don't actually know what's causing it, to be honest. I guess I'll also save that for next year.

Until then, Happy New Year!

Looks very amazing and promising. Happy new year!

Wow ! looking great - I bet it was nice to see the titlescreen nearly complete .

Those tiles near tales look like they need to be both flipped vertically AND mirrored horizontally?

Suprise!



Not only have I fixed the glitchy mess next to Tails, but I have also gotten tilemap scrolling working!

Turns out it was a glitch in the renderer all along. There's also a bug with drawing vertically flipped tiles, too. I'm still working on fixing it.

Unfortunately, the intro's background still doesn't work properly. This is mainly because it pulls out ALL the stops for the Master System's tilemap. It has vertically and/or horizontally flipped tiles, tiles drawn over sprites, and flipped tiles drawn over sprites. The only thing it DOESN'T use is background tiles that use the FG palette, but even the level intros use that.

Until I fix most of that, see you guys later!

I just took a glance at the code. Is all the code written by you—as in no libraries?

Aside from the original disassembly, I wrote everything myself. I did need some help with the tile converter, though.

Sprites! That's exciting for sure. Does the gameplay *work* at this time?

Pretty much. I don't have a fast solution to emulating the game's mappers right now, so it runs at 15-20 FPS. Also, a few levels have gimmicks that are still broken, like Sky High Zone's wind and Scrambled Egg Zone's pipes.

This looks fantastic so far!!!! Great job on all the progress, I'm excited to see what happens here in the future~

Good news, everyone! The game now runs at a playable 30-45 FPS!

This is all thanks to a relatively minor change, where the collision data, instead of being stored in one of twenty-seven 16KB appvars that have to be loaded in in its entirety, is loaded into the same 64KB range of RAM that the main engine is also loaded into. This saved about 24 million cycles each second!

There's only a few more things that have to be fixed before this project is complete, like some of the stage gimmicks. Until then, see you guys later!

This is amazing. I'm glad this is progressing so nicely as it has come a long way.

This is super impressive! Keep up the awesome work! I can't wait to give it a try when it's finished

Awesome! We needed a sonic game on the Ce.

Very impressive. I was surprised to learn the gba emulator for the ti nspire could run this, let alone the ce.

The final major milestone has been reached. I'm proud to announce that 8-bit Sonic 2 is now playable from start to finish on the 84+ CE!

And that's not all! Thanks to a hack of the original 8-bit Sonic 2 disassembly by pixelcat, I've been able to add something the original game really needed: The Spin Dash!



When I originally started this project, I didn't really care about 8-bit Sonic 2. The only reason I singled it out for porting in the first place was because it was the only one with a split disassembly. Now that I've learned all about this game inside and out, I've changed my tune.

Thanks to everyone that has helped me out, directly or indirectly, with this little project! It couldn't have been done without you guys.

Great work, congratulations

Version 1.00 of Sonic 2 CE is available now on Github!

This version adds, among other things, the iconic SEGA splash screen. This was only in the Game Gear version, as one was already in the Master System's BIOS.

Additionally, all image artifacting and flickering is now gone! This makes it a lot easier to see what is going on in the game, especially with the boss battles.

Since those were the last major issues with the port, this project is basically complete! If there's anything still wrong with the game, please let me know. I'll be sure to fix it in a future release.