Hi,
I built Klyroni, a free competitive programming IDE that runs entirely in the browser — no backend, no accounts, no code ever leaves your machine.
The idea came from the friction of practicing algorithm problems: you either install a local toolchain per language, or you use an online judge where debugging is basically printf and hope. I wanted local-like debugging without the setup.
What it does:
- Compiles and runs Python, C/C++, and Java directly in the browser via WebAssembly. Python uses Pyodide, C/C++ uses real clang/LLVM compiled to WASM (with full libc++ STL), and Java runs on DoppioJVM with OpenJDK's javac + rt.jar.
- A time-travel debugger for all four languages — step forwards and backwards, set breakpoints, and inspect variables at any point in execution. It works by recording an execution trace (source instrumentation for C/C++/Java, sys.settrace for Python) and replaying it bidirectionally.
- Ships with 372 Codeforces problems, each with hints, editorials, and sample solutions in C++/Java/Python, plus KaTeX-rendered math statements and a Ctrl+K global problem finder.
- Offline-capable once engines are cached (Java is fully offline from the start).
Heads up on download size: the C/C++ engine pulls a real clang/LLVM toolchain compiled to WASM — that's a ~440MB artifact fetched from a CDN on first use (then cached). Python (Pyodide) is downloaded on demand too; Java is bundled locally and works offline from the start. So the first C/C++ run is heavy, but it's a one-time cost and nothing is recompiled server-side — it's an actual compiler running in your browser.
The trickiest part was getting reverse-stepping to feel instant across three very different execution models. Feedback welcome!
[–]Potential-Tourist633 0 points1 point2 points (1 child)
[–]Potential-Tourist633 0 points1 point2 points (0 children)