Fewer Octop(i/uses/odes) than I would have expected
March 26, 2021 2:55 AM   Subscribe

Game Jams are, of course, not a new thing and there are plenty to choose from[itch.io] if you're looking to participate in one. But it's possible, likely even, that's you've never heard of Octojam.[itch.io] For the past seven years a small group of enthusiasts have spent the month of October writing games for the CHIP-8.

The CHIP-8[wikipedia] is, probably, the world's first Fantasy Console[lexaloffle.com] — a virtual machine designed specificially for writing video games — created decades before the PICO-8 coined and popularized the term.

Designed by Joseph Weisbecker[wikipedia] and first described in BYTE magazine[archive.org] in 1978, CHIP-8 features a simple(-ish) set of 35 machine instructions, including instructions for generating random numbers and displaying graphics on screen. Originally used on COSMAC VIP[wikipedia] 8-bit computers, it boasted a 64x32 pixel monochrome display, input via a 16 button keypad, and a whopping 4kB of addressable memory.

Eventually finding its way onto graphing calculators in the 80's, CHIP-8 interpreters were extended and modified[github] multiple times. The popular SuperChip, or S-CHIP, added a 128x64 pixel, toggleable, hi-res display and extended instruction set enabling programmers to scroll the display left, right, or down.

In 2014, John Earnest created online Integrated Development Environment (IDE) and high-level assembly language, Octo[github.io], for writing and compiling CHIP-8 programs. Along with Octo come the XO-CHIP extensions[github] including: audio buffer, up to 4 colour display, extravagantly spacious 64kB address space, and the ability to scroll UP!

While Octojam takes its name from Earnest's creation, authors are free to write CHIP-8, S-CHIP, or XO-CHIP games using any tools they wish, up to and including custom emulators/interpreters. There's certainly no shortage[github]: programmers interested in emulation[reddit] often tackle CHIP-8 as a first project.

Octojam (originally Octo-ber Jam) has, so far, had seven installments. The most recent offered two XO-CHIP game templates which contestants could tear apart and remix for their submissions: Into the GarlicScape[itch.io], a basic turn-based roguelike and Super NeatBox[itch.io], a simple platformer.

All previous Octojam pages: Sadly, it appears that not all previous submissions remain playable but you can find play-throughs and commentary for all seven Jams on youtube[playlist].

And yes, there is a CHIP-8 interpreter in PICO-8[lexaloffle.com]. Because of course there is.
posted by Mister_Sleight_of_Hand (2 comments total) 8 users marked this as a favorite
Given my interests and online social network, I'm surprised that I've never heard of this before. Wierd retro VMs keep popping up onto my feed and yet this is new to me.

Thanks for posting this.
posted by suetanvil at 7:05 AM on March 26, 2021 [1 favorite]

My dad used to get electronics magazines in the 80s, and I think one of them had a kit for a CHIP-8 machine; it was basically a bare board PC with a DIP-form-factor CPU and a keypad, and could have made a plausible prop bomb for a TV thriller. It didn't grab my attention because it looked terribly primitive compared to, say, Commodore 64s and such.
posted by acb at 8:10 AM on March 26, 2021 [1 favorite]

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