AI · alternatives · 2026

24 alternatives to Codex builds a working NES Emulator in one hour

Hi folks! I know NES emulators have been implemented countless times, in practically every language imaginable. However, having an LLM fully replicate the spec purely from memory—without referencing existing code—is still a significant challenge. It requires the underlying model to have strong anti-hallucination capabilities and solid long-term planning to keep from going astray. Because of this, building an NES emulator makes for an excellent LLM stress test. Here is how the emulator was built: Data Gathering: I asked Codex to download the necessary developer manuals and test suites. It was…

Below are 24 products that do a similar job, ranked by how close each is in meaning and then by launch-day votes.

1
My self-written hobby OS is finally running on my vintage IBM ThinkPad▲575
Finally got my hobby OS up and running on real hardware. I love the old IBM thinkpads, so thought it was the perfect machine to get it working on. Been working on it for quite some time now, but this has been a big milestone!
2025 · github.com · its alternatives →
2
I built a handheld CHIP-8 game console to teach myself embedded systems▲128
A while back I wrote a CHIP-8 emulator (which is considered the Hello, World! of emulators and is more accurately a virtual machine since historically CHIP-8 was an interpreted language running on top of the COSMAC VIP to make game programming easier). But a few months ago I got really interested in embedded software, so decided it would be neat to port my emulator to a STM32 MCU and design a console around it as a learning experience, since CHIP-8 never existed as a physical system. I didn't know much about embedded software when I began, and even less about electronics, but I managed to…
2022 · github.com · its alternatives →
3
Ghidra Plays Mario▲207
I've been exploring new ways of testing Ghidra processor modules. In this repo, I was able to emulate NES ROMs in Ghidra to test its 6502 specification, which resulted in finding and fixing some bugs. Context: Ghidra is used for reverse engineering binary executables, complementing the usual disassembly view with function decompilation. Each supported architecture has a SLEIGH specification, which provides semantics for parsing and emulating instructions, not unlike the dispatch handlers you would find in interpreters written for console emulators. Emulator devs have long had extensive test…
2023 · github.com · its alternatives →
4
An NES emulator written in Rust▲125
NES emulator written in Rust. Contribute to pcwalton/sprocketnes development by creating an account on GitHub.
2013 · github.com · its alternatives →
5
Cycle-accurate Nintendo NES emulator in ~1000 lines of code▲20
Compact cycle-accurate NES emulator. Contribute to AndreaOrru/LaiNES development by creating an account on GitHub.
2016 · github.com · its alternatives →
6
Replicas▲239
Hey HN! I'm Connor, creator of Replicas. I'm a heavy Codex/Claude Code user, and I wanted to hand off tasks to agents like I would to an engineer - kick something off before work, let it scaffold while I'm at lunch, even come back to a ready PR. The problem: existing alternatives use workspace VMs that are black boxes. I have no access to any of them - they can't run tests, read logs, or use tools like the Playwright MCP (which I use to verify agents actually fixed what they claim to fix). Replicas gives agents real cloud workspaces where they can: - Run your test suite and read the…
Jun 2026 · replicas.dev · its alternatives →
7
A cross-platform terminal emulator written in Java▲65
It's based on the jediterm library developed for IDEs, but it can also be put to work as a standalone terminal emulator with tabs. The library has been around for more than 10 years, but I don't think anyone made a terminal emulator app from it?
2025 · github.com · its alternatives →
8
I built a toy music controller for my 5yo with a coding agent▲37
The HN community may find the context of the prompts, organized by each turn in each session, the most useful. See the website/docs/prompts.md and session-X.md files. I also started exploring some workflows for the LLM to execute, organized in the website/docs/tasks/ folder. I found it pretty handy to have the LLM document our work as we went and simply embedded the static site into the executable, along with all the music and logic. The whole project took me about a day for the backend. The C++ controller itself took only a few turns. I enjoyed focusing on my son's…
2025 · github.com · its alternatives →
9IA
IronBoy, a highly accurate GameBoy emulator written in Rust, runs WASM▲33
Hey HN! Been working on this emulator on and off for the last couple years, and thought now would be a good time to try and show it off here. As far as unique features... I think this is the only online GameBoy emulator with support for save files? So there's your reason to exist, I guess. The WASM port was something I had in the back of my mind but I just kept putting it off because it seemed like it would've been a pain in the ass to implement, but all in all I think it took less than a week so that was a nice surprise!
2023 · nicolas-siplis.com · its alternatives →
10
A NES Emulator Written in Emacs Lisp▲10
A NES Emulator written in Emacs Lisp. Contribute to gongo/emacs-nes development by creating an account on GitHub.
2019 · github.com · its alternatives →
11
Made a e-4917 emulator with a short tutorial▲29
Creating a fantasy CPU emulator with React and TypeScript part 1
2021 · maartenhus.nl · its alternatives →
12
Building an LLM from Scratch in TypeScript▲33
The from-scratch guide to building large language models in NodeJS.
10d ago · book.humanexperiences.io · its alternatives →
13
LLM-powered NPCs running on your hardware▲24
Hey HN, My team is open-sourcing the inference stack and fined-tuned models we use to create LLM-powered NPCs: https://github.com/GigaxGames/gigax The generative agents paper [1] pioneered the idea of prompting LLMs to create autonomous NPCs. But existing implementations require multiple calls to an LLM to make the agent plan its day, chat with people, and interact with its environment [2]. Our approach allows NPCs to be stepped at runtime with a single pass on consumer-grade hardware, with reasonable latency. To achieve this, we've fine-tuned open-source LLMs [3] to…
2024 · github.com · its alternatives →
14
You Are Merlin – a Rust CLI and WASM Text Adventure Game▲12
This is my first Rust project which I got a bit carried away with. It was a great way to learn different parts of Rust and had jump some hurdles when building for WASM, like not having access to loops, std or DateTime. I'd appreciate any feedback of improvements, new features or themes to add. Thanks! Github: https://github.com/hseager/you-are-merlin
2024 · hseager.github.io · its alternatives →
15
Dungeon Master in Your Console▲14
I don't normally share side projects here(or in general). Don't have much time to open them up to too much attention. I started this project while riding in a car last weekend. Mainly to explore OpenAI Codex. Using Github mobile I wrote the initial specifications into the readme, and using the ChatGPT iOS app, had Codex build a simple CLI based dungeon master. Switched back to Github for managing the PRs and back and forth for the whole car ride... It kinda got a little out of hand from there, and it's now a mix of AI(mostly AI) and myself making adjustments... The first version was entirely…
2025 · github.com · its alternatives →
16
An LLM Running on a PS Vita▲5
Hello all, a couple of moons ago I ported karpathy's llama2.c code to run inference on the TinyStories 260K & 15M checkpoints on the on the PS Vita with the ability to download/delete the models on device. Runs showed that the 260K model ran at ~120 tok/s and at 15M ran at 1.8 tok/s, which probably could be a bit higher if it weren't a single threaded application. Had fun working on it as a weekend project, check it out for yourselves: https://github.com/callbacked/psvita-llm
2025 · github.com · its alternatives →
172P
2d platformer game built with Codex (zero code)▲10
Hi HN! On Sunday I spent a couple of hours building a short 2d platformer ("Prince of Persia" style). What's interesting is how I built it. I went for a zero-code approach, and built the whole thing using OpenAI Codex CLI and agent skills (with the progressive disclosure paradigm). You can play the game here: https://acatovic.github.io/gothicvania-codex-demo/ You can see the full code, agent skills and a complete writeup here: https://github.com/acatovic/gothicvania-codex-demo Some takeaways: * This was one of the most enjoyable experiences ever! *…
Feb 2026 · its alternatives →
18
I made my first NES emulator, written in Go▲6
NES emulator, written in Go. Contribute to scottferg/Fergulator development by creating an account on GitHub.
2012 · github.com · its alternatives →
19
Run any Llama model finetune and more, instantly▲7
Hi there, looking for feedback on my new project "Featherless.AI" The idea is to allow users to run all the models on hugging face instantly. Via the OpenAI API compatible endpoint. Why? Because its a real chore to download models and spin up GPUs, especially if you want to test multiple models. Not to mention GPUs cost multiple dollars an hour to rent. And if we want more people to use open source AI, we got to make it easier for them to try and play with all of them. So what if instead of spinning up dedicated GPUs per model (which is what every provider is doing) We can startup a LLM…
2024 · featherless.ai · its alternatives →
20
Plock: Use a local LLM from anywhere in your OS▲6
After seeing a cool demo of a hack on Twitter, I built a cross platform version of it that works well and uses streaming. From anywhere on Mac and Linux, trigger Ollama and optionally feed it your clipboard. I built it yesterday and it's already very useful to me. I'm pretty excited about it and wanted to share!
2024 · github.com · its alternatives →
21
Experiment ▴ LLM UI for developers with tool use visualization▲8
Hey HN! I built Experiment to solve a common frustration in LLM development: the lack of proper tools for prompt engineering experimentation. Here's what makes it different: Key Features: - Load and edit chat completion logs from CSV files - Fork and modify specific conversation entries - Run inference via Anthropic, Mistral, and OpenAI - Define custom tools using JSONSchema format - Visual tool usage analysis with collapsible, sorted key-value pairs - Full mobile support and available as installable PWA Technical Highlights: - Built with React using custom isomorphic architecture -…
2025 · github.com · its alternatives →
22
Python running on the Super Nintendo (in-browser demo)▲7
MicroPython (lexer, compiler and VM) on the SNES: 3.58 MHz 65816, 56 KB Python heap, 16-bit int. The REPL runs right inside the post via EmulatorJS and also works on real hardware via flashcart. I did this as a benchmark for Claude Fable. When the export ban hit, switching to Opus got the project stuck for three weeks; Fable came back and found the real bug in ninety minutes. Along the way: 23 compiler bugs and 4 MicroPython bugs, each root-caused with a minimal reproducer and filed upstream. If you run it on real hardware, I want a picture!
Jul 2026 · fabian-kuebler.com · its alternatives →
23
BlastEm – A highly accurate and moderately fast Genesis/MD emulator▲6
2017 · retrodev.com · its alternatives →
24
I built a tool to check if your computer can run LLMs locally▲8
Built a simple web app that tells you which open-source LLMs will work on your hardware. It auto-detects your specs, shows compatible models from Hugging Face, gives realistic performance estimates (tokens/sec), and recommends quantization settings. You can also manually input specs to see "what if I upgraded my RAM?" Made this after wasting time downloading giant models only to find they crawled on my hardware. Hope it saves you some frustration!
2025 · caniusellm.com · its alternatives →

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