The Lab

Machines you can watch work.

Two benches. One is a compute loop that has been running since July 2026 and has never been told to stop. The other is a code runner you can pick up and use, with no account and nothing to install.

Always on

One shared vCPU in AWS us-east-1. It sips CPU in fixed, tiny batches so the rest of the site never notices, saves its state to disk every few seconds, and picks up exactly where it left off across deploys and restarts. Nothing here is a simulation; the numbers on the home page are what the process has actually reached.

Segmented sieve

Hunting primes

The nth prime, the largest twin-prime pair found so far, and the gaps between them, recomputed continuously. Test any number of your own against it.

Hailstone sequences

The Collatz frontier

Every integer checked so far returns to 1. The frontier is how far that has been verified without a counterexample, alongside the number with the longest trajectory yet seen.

Write code, hit run

Three languages, three benches, because they do genuinely different things. Python and JavaScript execute on your own machine and never reach my server. Java cannot, so it compiles and runs inside a locked-down sandbox instead, and says so.

OpenJDK 21 · isolated sandbox

Java

Runs server-side with no network access, capped memory and CPU, and a hard timeout. The entry class is taken from your public class; no class, and it is compiled as Main.

CPython 3 via Pyodide (WebAssembly)

Python

A real CPython build compiled to WebAssembly, running in your tab. The standard library is there; sockets, subprocesses and the local filesystem are not.

Your browser's JS engine, in a Web Worker

Node

Modern JavaScript with console and timers, isolated in a worker. It is not Node itself; there is no require, fs or process, so Node's standard library is out of reach.

The compute engine once took the whole site down: an unbounded π spigot grew its BigInts until a single tick blocked the event loop for seconds. It now runs in fixed batches with hard caps, which is why it has been up continuously since. How the whole thing is put together.