sega-master-system-devkitsms

An agent skill by haroldo-ok, from haroldo-ok/sega-master-system-skill-for-claude. Tags: cli, debugging, development, game-development, optimization, sega-master-system.

What it does

Program, build, debug, and port Sega Master System (and Game Gear / SG-1000) homebrew games in C with devkitSMS (SMSlib + PSGlib) and the SDCC Z80 compiler. Use whenever the user writes, compiles, fixes, optimizes, or ports an SMS/Master System or Game Gear game or demo: the SDCC + devkitSMS toolchain; producing a `.sms`/`.gg` ROM; VDP tiles, the tilemap, hardware sprites, palettes, PSG music/SFX, joypad input, VBlank/line interrupts, ROM bank switching, SRAM saves; converting assets (`.psgcompr` tiles, `vgm2psg` music, `folder2c`/`assets2banks`); or debugging the classic "compiles but boots to a black screen" failure. Trigger on mentions of devkitSMS, SMSlib, PSGlib, SDCC `-mz80`, ihx2sms, crt0_sms, `SMS_addSprite`/`SMS_waitForVBlank`, a `.sms` ROM, Master System / Game Gear homebrew, or Haroldo-OK's SMS games (Jill of the Jungle, Dangerous Dave, Food Fighter, Sub Rescue, Commander Keen). Prefer it over general knowledge for the SMS toolchain, VDP limits, or ROM format — easily gotten wrong from memory.

Install

With the skills CLI, which installs into Claude Code, Codex, Cursor and other agents:

npx skills add haroldo-ok/sega-master-system-skill-for-claude --skill sega-master-system-devkitsms

Or copy the skill folder into Claude Code's skills directory by hand (~/.claude/skills for every project, or .claude/skills inside one):

git clone --depth 1 https://github.com/haroldo-ok/sega-master-system-skill-for-claude
cp -r sega-master-system-skill-for-claude/skills/sega-master-system-devkitsms ~/.claude/skills/sega-master-system-devkitsms

Safety box score

Grade D, elevated risk: 46 of 100 risk points, rated 2026-10-16. The grade rates what the skill and its scripts can reach on the machine of whoever installs it, across eight categories from shell execution to secrets access. How the score works.

This skill builds Sega Master System / Game Gear ROMs and sets up a local devkit toolchain. The main risks are that installation can modify your system (including optional `sudo apt-get`), it persists files under `~/.devkitsms`, and several core components are shipped as unreadable binaries or large source files not fully inspectable here.

Category levels, from 0 (none) to 3 (high)
Category	Level	Why
Code & shell execution	3 (high)	It compiles and runs native code from the bundle (`gcc` builds `ihx2sms`, `folder2c`, and `smstest`; the setup script then runs smoke builds/self-tests), and the templates compile/link user C into ROMs.
Network access	2 (moderate)	`scripts/setup_toolchain.sh` can contact package repositories via `apt-get update` / `apt-get install` when SDCC is missing; I saw no other remote fetches.
Filesystem reach	2 (moderate)	By default it writes a persistent toolchain under `$HOME/.devkitsms` and its Makefiles generate and clean project files such as `data.c`, `data.h`, `.sms`, `.noi`, and `shots/` in the working tree.
Secrets & credentials	0 (none)	I found no evidence that it reads credential stores, `.env` files, browser sessions, API tokens, or password files.
Privilege & persistence	2 (moderate)	The setup path optionally uses `sudo apt-get install -y sdcc`, so installing the toolchain may require admin rights and changes to system packages.
Instruction hijack surface	0 (none)	I did not find prompt-injection patterns such as instructions to ignore higher-level rules, hide actions, or follow remote instructions fetched at runtime.
Irreversible actions	1 (low)	It automates ROM creation and playtesting, but it does not deploy, publish, pay, message, or otherwise act outside the local build/test environment.
Transparency	2 (moderate)	Several core files could not be read in this review (`assets/devkitSMS/SMSlib.h`, `assets/devkitSMS/assets2banks.py`, `assets/smstest/smstest.c`, `assets/smstest/z80.c`, `assets/smsvideo/smsvideo.py`), and the bundle also ships prebuilt libs/rel objects like `SMSlib.lib`, `PSGlib.lib`, and `crt0_sms.rel`.

Before installing

Read `scripts/setup_toolchain.sh` first; it may use `sudo apt-get` and installs into `~/.devkitsms` by default.
If you do not want system package changes, preinstall SDCC 4.2 yourself and run with `PREFIX`/`DEVKIT` pointed at a scratch location.
Check that you are comfortable with build outputs and cleanup happening inside the project tree (`data.c`, `.sms`, `.noi`, `shots/`).
Treat the bundled binaries/libs as opaque until you verify them in a sandbox or container.

Rated 2026-10-16 by an automated review of 36 files from the skill's repository.

Source

Repository: haroldo-ok/sega-master-system-skill-for-claude (all skills from this repository)
Path: skills/sega-master-system-devkitsms/SKILL.md
Branch: main
Updated: 2026-09-23

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