Raphael Stäbler · Frankfurt, Germany
I've been writing software for more than 20 years, these days mostly web and mobile apps. Production Build is my company. This is the personal side: boards I designed, the drivers that run them, games, web tools, a blog and a book.
Printed circuit boards and FPGA logic: the layer you can hold in your hand.
U1 L1 Started 2021
An FPGA handheld that plays original Game Boy cartridges
Two custom KiCad boards around a Xilinx Spartan-7, plus the Verilog for display, UART, video buffer, PWM and debugging. The Game Boy core itself (CPU, PPU, sound) comes from Wenting Zhang's VerilogBoy.
Code that runs on the hardware itself: a display driver and a Game Boy emulator on a microcontroller.
FW1 L2L1 Started 2020
A display module and the library that drives it
The Arduino library for a 4-inch, 480×480 TFT module built around an FT81x graphics controller (FT813): up to 24-bit colour, built-in fonts and widgets, JPEG/PNG decoding and audio, tested on Uno, Nano, Nano Every, Due, ESP32 and Teensy 4.0. The module is open hardware, certified by OSHWA as DE000089, and was sold on Tindie. A Python port for the Raspberry Pi 5 exists too.
FW2 L2 Started 2019
A Game Boy emulator on a Teensy 4.1
Work in progress: it runs Tetris, passes Blargg's CPU instruction tests, has 4-channel audio, loads ROMs from SD card and draws to the FT81x display. With substantial contributions by @granthaack.
Things you install on a phone: a puzzle game with a built-in AI and a fantasy sports manager.
A1 L3 Started 2022
A match-three game with an AI that plays for you
Built with Flutter and Flame. From level 6, a reinforcement-learning agent can take over, running on the phone as a TensorFlow Lite model. No ads, no in-app purchases, no tracking. On Android now, iOS coming soon.
A2 L3 Started 2026
Unofficial fantasy soccer and ice hockey for Switzerland
Pick a squad under a salary cap, set your lineup and watch the points move while the matches are played. Both sports run on one codebase: a NestJS API with a replayable live-season engine, a Flutter app and an Eleventy website.
Web products, small tools and data experiments that live in a browser or a terminal.
W1 L4 Started 2026
Your circuit board, as art
Turns the Gerber files of your circuit board into art: drop them in, pick a style such as Neon, Exploded, Ink wash, Linocut or Patch, and download the image. The Gerbers are parsed by Python (Pyodide and gerbonara) right in your browser, so your files are never uploaded. Works with KiCad, Altium, Eagle, EasyEDA and most other tools.
W2 L4 Started 2023
Analytics for Mastodon accounts
Engagement and follower growth for your Mastodon account. Open source and self-hostable with prebuilt Docker images: a TypeScript monorepo with a NestJS API, a Remix frontend and a CLI worker.
W3 L4 Started 2026
About 90 years of daily Frankfurt temperatures, one ring per year
Daily temperatures from DWD station 1420 (Frankfurt/Main) and MeteoSwiss Zürich/Fluntern, drawn raw, without smoothing, as one closed ring per year. Step through the decades or compare two of them.
W4 L4 Started 2025
Conway's Game of Life, run backwards
A Python CLI that finds predecessor states with a SAT solver. For Garden-of-Eden patterns, which have no predecessor, it searches for the closest pattern that can be reversed. The picture is from a separate Game of Life simulation I rendered in Blender.
The top of the stack is paper: a workbook generated from data and typeset by code.
P1 L5 Started 2026
A Japanese reading workbook, typeset by a Python pipeline
315 A4 pages for German speakers learning to read Japanese, focused on reading speed rather than copying characters: timed kana drills (432 words, 392 sentences), all 103 N5 kanji with a double page each, answers and a speed tracker. Book and cover are generated from JSON data with reportlab; validators check the data against KANJIDIC2 and JMdict.
Blog