Penumbra Tech
[Projects—]

Live, exercisable evidence.

Each project below is either shipped as a real product you can install, or running right now and you can click into it. A few require sign-in (free, no spam) — that's because they save data to the database, which only makes sense per-user.

15 projects

Products

Shipped, downloadable software — Steam releases and installable Windows apps under the Penumbra family of studios.

3 projects

Client work

Paid engagements with named outside clients.

1 project

Infrastructure & SaaS

The plumbing — load testing, payments, deploys, SaaS rescue patterns.

3 projects

Web apps

Full-stack web apps with auth, MySQL, and the seams that always need work.

3 projects

Study tools

Two free, open-source study apps I built and gave away — no signup, no backend, fully offline, progress saved in your browser. A beginner on-ramp into discrete math, and its advanced follow-up for a theory-of-computation course. Launch either in the browser or read the source.

2 projects
① Start here
Free · Open source · Offline · No signup

Toddler to Turing

Discrete math from scratch — from “what does ∀ even mean?” to understanding a Turing machine.

A gentle, gamified on-ramp into the discrete-math foundations of computer science, for anyone the notation has ever scared off. Eight gated modules — Symbols & Notation, Logic, Sets, Functions & Relations, Proofs & Induction, Strings & Languages, Graphs, and Machines & Algorithms — with 146 auto-graded questions, spaced repetition, plain-English “explain like I’m five” walkthroughs, Venn / graph / state-machine diagrams, a printable cheat sheet, and a timed quiz. Fully offline; progress saves in your browser. It ends by handing you off to the Theory of Computation review app.

Vanilla JSKaTeX8 gated modules146 questionsSpaced repetitionOffline-first
② Follow-up
Free · Open source · Offline · Sipser 3rd ed.

Theory of Computation Review

An 859-question spaced-repetition review app for a Theory of Computation course (Sipser, 3rd ed.).

The advanced follow-up: comprehensive final-exam prep covering Sipser Chapters 0–8 plus exam checkpoints — regular & context-free languages, Turing machines, decidability, reducibility, and time & space complexity. Auto-graded questions on a custom Leitner + streak + mastery-gated scheduler, real-world discussion questions, DFA / NFA / TM state-diagram practice, a timed mock-exam mode, and a reference cheat sheet. Built to prove I can reason about computability and complexity, not just stitch libraries. A themed build also runs on this site at /toc/.

Vanilla JSKaTeX859 questionsMastery-gated SRSMock-exam modeDFA / NFA / TM diagrams

Computer science & tools

Pure-craft work: zero-dependency, single-file browser tools built from scratch.

1 project
Single-file web app · Open source

Penumbra Music Visualizer

I wanted a music visualizer that survived bad wifi at a party — no install, no cookies, no signup, no cloud dependency, just one HTML file you double-click. Drag a song onto it and nine reactive visualizers light up (three Penumbra-branded, six conventional spectrum treatments). From-scratch BPM detection via onset-envelope autocorrelation, musical-key detection via Krumhansl-Schmuckler chroma — both cached in localStorage so each song is analyzed once. Tab-audio capture lets it visualize YouTube Music or Spotify; built-in canvas+audio recorder exports a .webm. Zero dependencies, no build step, ~52KB of one index.html.

Single-file HTMLWeb Audio APICanvas 2DFFT / BPM / Key detectionlocalStorage cacheMediaRecorder
Open source · MIT · Download index.html, double-click
Open the project →

Source & documentation

Where to read the actual code and the public API.

2 projects

See something close to your problem?

Most engagements start with a 30-minute call. Quick sketch of the problem, honest answer on whether I'm the right person for it, and a rough shape of the work.