Writing
- Family treeFree, no tracking, no data collected: build a family tree and print it on A4, also in Polish
- SubtleCrypto playgroundGenerate keys, hash, encrypt, sign, derive and wrap with Web Crypto
- Option Trade Lab formulasEvery Black-Scholes formula behind the lab, with a worked example
- Explain the optionDescribe one option position in plain words, with P&L at expiry
- Read the ticketA drill for decoding option positions from broker notation
- SFFE, a fast math expression evaluatorHow a parse-once, evaluate-forever C interpreter is built
- Mortgage loan calculationDeriving the fixed monthly payment formula, also available in Polish
- Quadratic Bezier curve lengthA closed-form derivation of the arc length integral
- Curb your egoNotes from a side project that did not work out
printu.plPhoto books, calendars, posters and canvas prints from your own photos, designed in an online editor. Polish market.
annotely.comAnnotate any screenshot in the browser: arrows, shapes, highlights and blur, with no install or sign-up.
scribblepadgames.comClassic pen-and-paper games as printed notepads or print-at-home PDFs. No screens, no ads.