u/JumpFast

Built Anvil, a LeetCode/NeetCode-style practice app with lessons for actually learning patterns instead of memorizing solutions. Works fully offline. Backend/desktop shell built with Tauri (Rust), so it's lightweight and fast. Supports Python and JS for solving problems.

Free and open source, would love feedback or contributors, especially on the Rust side.

🔗 Download: https://github.com/kudzaiprichard/anvil-releases/releases
🔗 Source: https://github.com/kudzaiprichard/anvil

PS: this is my first time doing an open source project so please do tell me what you think

Most coding challenge platforms assume you have a constant internet connection. While building an offline coding practice environment, I ran into a few interesting engineering problems:

1. Building a reliable offline judge

Traditional coding platforms often compare program output against predefined test cases. The problem is that this can be fragile and doesn't always verify whether a solution is actually correct.

For Anvil, I experimented with an oracle-based judging approach:

• A reference solution generates expected behavior
• A brute-force implementation acts as an independent correctness check
• User submissions are evaluated against generated cases rather than only static outputs

The goal was to make it harder for incorrect solutions to pass due to incomplete test coverage.

2. Running multiple languages locally

Supporting JavaScript and Python offline introduced challenges around:

• Process isolation
• Execution time limits
• Memory constraints
• Handling runtime failures consistently across languages

3. Making learning part of problem solving

Another challenge was designing a system where solving problems also reinforces pattern recognition. Instead of only storing solved problems, I added structured explanations, visualizations, and spaced repetition using FSRS to revisit concepts over time.

The result is Anvil, an open-source offline coding practice environment for JavaScript and Python.

Source:
https://github.com/kudzaiprichard/anvil

Releases:
https://github.com/kudzaiprichard/anvil-releases/releases

I'm interested in feedback from people who have built coding platforms, judges, sandboxed execution systems, or learning tools. What approaches would you take differently?

Most LeetCode-style platforms require an internet connection. I wanted to build one that delivers the full experience completely offline, while also helping you get better at recognizing patterns as you solve.

So I built Anvil.

• 💻 Fully offline coding platform for JavaScript and Python
• 🧩 Solve LeetCode-style problems while learning the underlying patterns through structured lessons, visualizations, and pattern-recognition drills
• 🛡 Robust judging powered by a reference implementation and brute-force oracle instead of relying solely on static expected outputs
• 🔁 FSRS spaced repetition to reinforce patterns over time
• 🔒 No account, no telemetry, no AI copilot—just you and the problem

It's free, MIT licensed, and runs on Windows, macOS, and Linux.

Releases:
https://github.com/kudzaiprichard/anvil-releases/releases

Source:
https://github.com/kudzaiprichard/anvil

Whether you enjoy grinding LeetCode for fun, are working through NeetCode/DSA, or are preparing for technical interviews, I'd love to hear what you think and what could make it better.

If you're an open-source contributor, I'd also love help with problems, features, documentation, testing, UI improvements, or the judge. Contributions of any size are welcome.

Most LeetCode-style platforms require an internet connection. I wanted to build one that delivers the full experience completely offline, while also helping you get better at recognizing patterns as you solve.

So I built Anvil.

• 💻 Fully offline coding platform for JavaScript and Python
• 🧩 Solve LeetCode-style problems while learning the underlying patterns through structured lessons, visualizations, and pattern-recognition drills
• 🛡 Robust judging powered by a reference implementation and brute-force oracle instead of relying solely on static expected outputs
• 🔁 FSRS spaced repetition to reinforce patterns over time
• 🔒 No account, no telemetry, no AI copilot—just you and the problem

It's free, MIT licensed, and runs on Windows, macOS, and Linux.

Releases:
https://github.com/kudzaiprichard/anvil-releases/releases

Source:
https://github.com/kudzaiprichard/anvil

Whether you enjoy grinding LeetCode for fun, are working through NeetCode/DSA, or are preparing for technical interviews, I'd love to hear what you think and what could make it better.

If you're an open-source contributor, I'd also love help with problems, features, documentation, testing, UI improvements, or the judge. Contributions of any size are welcome.

Most LeetCode-style platforms require an internet connection. I wanted to build one that delivers the full experience completely offline, while also helping you get better at recognizing patterns as you solve.

So I built Anvil.

• 💻 Fully offline coding platform for JavaScript and Python
• 🧩 Solve LeetCode-style problems while learning the underlying patterns through structured lessons, visualizations, and pattern-recognition drills
• 🛡 Robust judging powered by a reference implementation and brute-force oracle instead of relying solely on static expected outputs
• 🔁 FSRS spaced repetition to reinforce patterns over time
• 🔒 No account, no telemetry, no AI copilot—just you and the problem

It's free, MIT licensed, and runs on Windows, macOS, and Linux.

Releases:
https://github.com/kudzaiprichard/anvil-releases/releases

Source:
https://github.com/kudzaiprichard/anvil

Whether you enjoy grinding LeetCode for fun, are working through NeetCode/DSA, or are preparing for technical interviews, I'd love to hear what you think and what could make it better.

If you're an open-source contributor, I'd also love help with problems, features, documentation, testing, UI improvements, or the judge. Contributions of any size are welcome.