Homebrew coder builds a Zelda-style SNES game entirely in hand-written assembly

A solo developer known as Inkbox is building a top-down SNES adventure game in raw 65816 assembly, sharing the process and a sound engine on GitHub.

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A developer going by Inkbox is writing a full Super Nintendo game by hand, in assembly, with no engine to lean on. The project, a top-down adventure in the mould of Zelda, is documented in a series of videos that walk through how the SNES actually works at the level of registers and memory maps, as reported by Hackaday.

That is a harder path than it sounds. Modern homebrew tends to lean on higher level tools, or at least on established libraries, to avoid the SNES's stranger corners. Inkbox is doing neither. According to Hackaday, the project is constrained to two 64 kB RAM banks and a 3.58 MHz Ricoh CPU that the site describes as 6502 based, referring to the 65816 chip at the SNES's heart, an extended cousin of the classic 6502. Inkbox has also set himself a 4 MB cartridge limit to match what a game released in the console's actual working life would have shipped on, which Hackaday calls claustrophobic by today's standards. It is worth remembering that some commercial SNES titles pushed well past that ceiling by the system's later years, so the self-imposed limit is as much a discipline as a hardware wall.

Why doing it by hand matters

Writing directly in assembly means Inkbox has to manage the SNES's graphics modes, sprite handling and audio registers without any abstraction layer doing the bookkeeping. Hackaday notes the videos cover everything from the different background graphics modes to which registers drive sound, alongside a walk through HDMA, the SNES's horizontal blank direct memory access system that lets a program change graphics settings line by line as the screen draws, which is how the console pulled off tricks like parallax scrolling and gradient skies on hardware with no dedicated layer for either.

The result, if it lands, is a game built the way SNES developers actually worked in the early 1990s: register by register, cycle by cycle, with every trick justified by a real hardware constraint rather than an engine default. That is the appeal for the audience Hackaday is clearly writing for, people who want to understand the machine rather than just play something that runs on it.

What is public already

Inkbox has released the SNES Sound Engine behind the project as open source on GitHub, which Hackaday singles out as useful groundwork for anyone else attempting SNES homebrew, since sound driver code is one of the fiddlier parts of the platform to get right from scratch. The game itself is already up on itch.io on a pay-what-you-want basis, though it is described as a work in progress rather than a finished release. Hackaday also mentions that Inkbox has form outside the SNES, having done comparable low-level work in x86 assembly.

What is still unclear

There is no confirmed release date for a finished version of the adventure game, and Hackaday's coverage is based on the video series rather than a hands-on build, so claims about performance and scope come from the developer's own demonstration rather than independent testing. How complete the sound engine is, and whether it will be maintained as a general purpose tool for other homebrew projects, is also not addressed in the reporting. For now the project is a working demonstration of how much can still be squeezed out of thirty-year-old silicon by someone willing to write every instruction themselves, discussed further in the r/retrogamedev thread.

Sources

Image: Hackaday

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