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Educational implementation of NES emulator in Kotlin, based on Java vNES emulator
- Forks
- 4
- Last pushed
- Updated Sep 2026
Repo stats from the GitHub API, cached Oct 2026.
CommunityJev Demos & Experiments
kNES
Kotlin NES emulator whose agent plays Super Mario Bros. and Final Fantasy through typed decisions. Each turn becomes one Choice over goals that can actually run, wired through SemIf against a local Qwen3.5-4B, so a button the game does not offer is never an option; 900 logged decisions never answered off-menu.
- Stars
- 34
- Language
- Kotlin
- License
- GPL-3.0
- Published by
- Community
- Last verified
- Oct 2026
About this project
kNES is a Nintendo Entertainment System (NES) emulator written in Kotlin, forked from the vNES Java emulator. This project was created primarily for fun and educational purposes, allowing developers to learn about emulation techniques and NES hardware while enjoying classic games. kNES is a reimplementation and extension of the vNES emulator (originally developed by Brian F. R.) in Kotlin. The project aims to: Provide a modern, Kotlin-based NES emulator.
Quoted from the project's README. Read the full README.
Used inJev for Gaming
- Capabilities
- Open sourceRuns locallySelf-hosted
Highlights
- Agent access ships two ways: an MCP server with 14 tools and a REST API on port 6502 with 12 endpoints.
- 900 decisions at about 400ms each on an M5 Pro never picked an option off the declared menu.
- Core emulator passes the nestest official and unofficial opcode suites within 800+ automated tests.
- Game knowledge lives in profiles/*.json, so teaching another game is a JSON edit, not code.
Watch out
GPL-3.0 licensed and forked from the vNES Java emulator, so the emulator lineage carries that license. The typed-decision agent path needs a local Qwen3.5-4B through SemIf or one OPENAI_API_KEY, and tests that need commercial ROMs skip themselves when roms/ is absent.
Questions about this entry
Short answers drawn from the linked project or page.
The goals that can apply this turn become the declared options of one typed Choice through SemIf, the open implementation of the Jev interface. A button the game does not offer was never on the menu, so it cannot be selected, unlike free-form JSON generation.
Yes. knes-agent runs campaigns against Final Fantasy and Super Mario Bros from a cold boot, creating a party and buying a weapon with no human input, using either OPENAI_API_KEY or GEMINI_API_KEY, or the local SemIf model through tools/live_demo.sh.
GPL-3.0, forked from the vNES Java emulator, so the emulator lineage carries that license. Every module targets Java 17, and Gradle 9.4+ is provided through the wrapper.
Mapper 0 (NROM) and Mapper 1 (MMC1/SxROM) are implemented, covering titles like Super Mario Bros, Zelda, Metroid and Mega Man 2. A ROM with any other mapper still loads on an NROM substitute, but NES.isMapperSupported and the load_rom message report it instead of substituting silently.
Java 17 and the bundled Gradle wrapper: ./gradlew build, then ./gradlew run, which lets you choose between the Compose, Skiko and terminal UIs. The Compose Desktop UI is the primary, recommended one.
Two ways: an MCP server with fourteen tools such as load_rom, step, tap, sequence, observe and apply_profile, and a headless REST API on port 6502 with twelve endpoints including /step, /screen, /state, /watch, /press, /release and /fm2.
Phase rules, landmark anchors and the signals tools ask about live in profiles/<id>.json rather than in the agent, so teaching another game is a JSON edit rather than a code change.
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