Gearcoleco
Gearcoleco is a very accurate, cross-platform ColecoVision emulator written in C++ that runs on Windows, macOS, Linux, BSD and RetroArch, with an embedded MCP server for AI debugging and development.
This is an open source project with its ongoing development made possible thanks to the support by these awesome backers. If you find it useful, please consider sponsoring.
Don't hesitate to report bugs or ask for new features by opening an issue.
Downloads
Notes:
Features
- Very accurate Z80 core, TMS9918 VDP, SN76489 PSG and AY-3-8910 SGM emulation.
- Support for ColecoVision Super Game Module (SGM) and MegaCart ROMs.
- Support for Super Action Controller (SAC), Wheel Controller and Roller Controller.
- Save states with preview and rewind support.
- Run-ahead support to reduce input latency.
- Compressed ROM support (ZIP).
- VGM recorder.
- Supported platforms (standalone): Windows, Linux, BSD and macOS.
- Supported platforms (libretro): Windows, Linux, macOS, Raspberry Pi, Android, iOS, tvOS, webOS, PlayStation Vita, PlayStation 3, Nintendo 3DS, Nintendo GameCube, Nintendo Wii, Nintendo WiiU, Nintendo Switch, Emscripten, Classic Mini systems (NES, SNES, C64, ...), OpenDingux, RetroFW and QNX.
- Full debugger with just-in-time disassembler, CPU breakpoints, memory access breakpoints, code navigation (goto address, JP JR and CALL double clicking), debug symbols, automatic labels, memory editor, trace logger, IO inspector and VRAM viewer including registers, tiles, sprites and backgrounds.
- MCP server for AI-assisted debugging with GitHub Copilot, Claude, Codex and similar, exposing tools for execution control, memory inspection, hardware status, rewind and more.
- Windows, Linux and macOS Portable Mode.
- Programmable Shader Chain.
- ROM loading from the command line by adding the ROM path as an argument.
- ROM loading using drag & drop.
- Support for modern game controllers through gamecontrollerdb.txt file located in the same directory as the application binary.
Tips
Basic Usage
- BIOS: Gearcoleco needs a BIOS to run. It is possible to load any BIOS but the original one with md5
2c66f5911e5b42b8ebe113403548eee7 is recommended.
- Spinners: When using any kind of spinner it is useful to capture the mouse by pressing
F12. It is also recommended to disable spinners for software that don't use them.
- Rewind: Hold the configured rewind hotkey (
Backspace by default) or a mapped gamepad shortcut to step backwards through recent gameplay.
- Overscan: For a precise representation of the original image, select Overscan
Top+Bottom and Aspect Ratio Standard (4:3 DAR) in the Video menu.
- Mouse Cursor: Automatically hides when hovering over the main output window or when Main Menu is disabled.
- Portable Mode: Run with
--portable, or create an empty file named portable.ini in the same directory as the application binary. On macOS, place the file next to the .app bundle.
Debugging Features
- Docking Windows: In debug mode, you can dock windows together by pressing SHIFT and dragging a window onto another.
- Multi-viewport: In Windows or macOS, you can enable "multi-viewport" in the debug menu. You must restart the emulator for the change to take effect. Once enabled, you can drag debugger windows outside the main window.
- Single Instance: You can enable "Single Instance" in the
Emulator menu. When enabled, opening a ROM while another instance is running will send the ROM to the running instance instead of starting a new one.
- Debug Symbols: The emulator automatically tries to load a symbol file when loading a ROM (.sym, .noi). For example, for
path_to_rom_file.rom it tries to load path_to_rom_file.sym. You can also load a symbol file using the GUI or the CLI. It supports SDCC/NoICE (.noi), wla-dx and vasm/generic file formats.
- Rewind Scrubbing: In debug mode, pause emulation and open the Rewind window to scrub through captured snapshots.
Command Line Usage
gearcoleco [options] [rom_file] [symbol_file]
Arguments:
[rom_file] ROM file: accepts ROMs (.col, .cv, .rom, .bin) or ZIP (.zip)
[symbol_file] Optional symbol file for debugging
Options:
-f, --fullscreen Start in fullscreen mode
-w, --windowed Start in windowed mode with menu visible
--mcp-stdio Auto-start MCP server with stdio transport
--mcp-http Auto-start MCP server with HTTP transport
--mcp-router Enable compact MCP tool routing
--mcp-http-address A HTTP bind address (default: 127.0.0.1)
--mcp-http-port N HTTP port for MCP server (default: 7777)
--headless Run without GUI (requires --mcp-stdio or --mcp-http)
--portable Store configuration and user data beside the application
-v, --version Display version information
-h, --help Display this help message
MCP Server
Gearcoleco includes a Model Context Protocol (MCP) server that enables AI-assisted debugging through AI agents like GitHub Copilot, Claude, Codex and similar. The server provides tools for execution control, memory inspection, breakpoints, disassembly, hardware status, and more. STDIO and HTTP transports are supported, with STDIO preferred.
For complete setup instructions and tool documentation, see MCP_README.md.
Agent Skills
Gearcoleco provides Agent Skills that teach AI assistants how to effectively use the emulator for specific tasks:
- gearcoleco-debugging — Game debugging, code tracing, breakpoint management, hardware inspection, and reverse engineering.
- gearcoleco-romhacking — Cheat creation, memory searching, ROM data modification, text translation, and game patching.
Install with npx skills add drhelius/gearcoleco. See the skills README for details.
Build Instructions
Windows
- Install Microsoft Visual Studio Community 2026 or later.
- Download the latest SDL3 VC development libraries from SDL3 Releases (the file named
SDL3-devel-x.y.z-VC.zip).
- Extract the archive and rename the resulting folder (e.g.
SDL3-x.y.z) to SDL3.
- Place the
SDL3 folder inside platforms/windows/dependencies/ so that the include path is platforms/windows/dependencies/SDL3/include/SDL3/.
- Open the Gearcoleco Visual Studio solution
platforms/windows/Gearcoleco.sln and build.
macOS
- Install Xcode and run
xcode-select --install in the terminal for the compiler to be available on the command line.
- Run these commands to generate a Mac app bundle:
brew install sdl3
cd platforms/macos
make dist
Linux
- Ubuntu / Debian / Raspberry Pi (Raspbian):
If you are using Ubuntu 25.04 or later, you can install SDL3 directly. Use the following commands to build:
sudo apt install build-essential libsdl3-dev
cd platforms/linux
make
For older Ubuntu versions (22.04, 24.04), you need to build SDL3 from source first. Use the following commands to build both SDL3 and Gearcoleco:
sudo apt install build-essential cmake git curl jq pkg-config \
libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxfixes-dev \
libxi-dev libxss-dev libxkbcommon-dev libwayland-dev libdecor-0-dev \
libdrm-dev libgbm-dev libgl1-mesa-dev libegl1-mesa-dev libdbus-1-dev libudev-dev libxtst-dev
SDL3_TAG=$(curl -s https://api.github.com/repos/libsdl-org/SDL/releases/latest | jq -r '.tag_name')
git clone --depth 1 --branch "$SDL3_TAG" https://github.com/libsdl-org/SDL.git /tmp/SDL3
cmake -S /tmp/SDL3 -B /tmp/SDL3/build -DCMAKE_INSTALL_PREFIX=/usr -DSDL_TESTS=OFF -DSDL_EXAMPLES=OFF
cmake --build /tmp/SDL3/build -j$(nproc)
sudo cmake --install /tmp/SDL3/build
cd platforms/linux
make
sudo dnf install @development-tools gcc-c++ SDL3-devel
cd platforms/linux
make
sudo pacman -S base-devel sdl3
cd platforms/linux
make
BSD
su root -c "pkg install -y git gmake pkgconf sdl3"
cd platforms/bsd
USE_CLANG=1 gmake
su root -c "pkgin install gmake pkgconf SDL3"
cd platforms/bsd
gmake
doas pkg_add gmake sdl3
cd platforms/bsd
LDFLAGS=-L/usr/X11R6/lib/ USE_CLANG=1 gmake
Libretro
- Ubuntu / Debian / Raspberry Pi (Raspbian):
sudo apt install build-essential
cd platforms/libretro
make
sudo dnf install @development-tools gcc-c++
cd platforms/libretro
make
Screenshots
Contributors
Thank you to all the people who have already contributed to Gearcoleco!
License
Gearcoleco is licensed under the GNU General Public License v3.0 License, see LICENSE for more information.