// software engineer · 20+ years

Hi, I'm Caleb Cohoon.
I build things that ship.

From Palm Pilot web apps to a Nintendo 64 game engine, from e‑commerce platforms to a high‑altitude balloon beaming photos over LoRa — and most recently, a chip taped out on real silicon. Two decades in, I still build for the fun of it.

See my work Get in touch

caleb@cohoon: ~

$ whoami
caleb — software engineer

$ uptime
20+ years building, still going

$ ls ~/shipped-on
web/      ios/      dotnet/   rails/
arduino/  palm/     n64/      dreamcast/
nds/      msdos/    rpi/      silicon/

$ █

01 Featured Projects

Personal work, built nights and weekends — source available on GitHub where noted.

UltraEd level editor showing a 3D scene, scene graph, and property panels

2017–2022★ 139 on GitHub

UltraEd — Nintendo 64 Game Engine & Level Editor

A from-scratch level editor and game engine targeting real Nintendo 64 hardware. Scene editing, automatic asset tracking, and a C scripting API with actor lifecycle hooks ($Start, $Update, $Input, $Collide). Builds run in the bundled cen64 emulator or on a console via the 64drive flash cart. Featured on the Hacker News front page and listed in the community-curated Awesome N64 Development index.

C
DirectX
N64
Compilers & tooling

Source Show HN (90 points)

2006★ Original paper included

S.A.D — A GPS Speed Awareness Device

A homebrew device that tells you the speed limit of the road you're on — built years before cars did this themselves. A floor-mounted base unit reads its position from a GPS module, parses the raw NMEA 0183 stream, and matches your coordinates against street “boundary boxes” stored in an I²C EEPROM, then beams the speed limit and street name to a dashboard LCD over a single phone cable.

The base runs four different Atmel 8051 microcontrollers — one parsing GPS, one matching the map, one handling EEPROM map updates over a DB9 serial link from a custom PC tool, and one driving the remote display. Each chip model (AT89C2051/51/52/55) was picked to fit its code module. All of it hand-wired on breadboards and stuffed into a project box.

C
8051 / assembly
GPS / NMEA
I²C EEPROM
Embedded

Read the original paper (PDF)

The finished S.A.D — a black project-box base unit with status LEDs and three red buttons, above a separate dashboard LCD module — // the finished S.A.D — base unit and dashboard LCD

Inside the base unit — a dense rat's nest of colored jumper wires across breadboards, with the silver GPS module at lower right — // base unit internals — GPS module at lower right

The dashboard LCD module: a character LCD soldered to a small board, wired across a breadboard, base unit behind it — // the remote LCD module, fed serially over RJ-11

Animated first-person scene from fragment, a 1.4 MB interactive demo

2022

fragment — A World on a Floppy Disk

A demoscene-style experiment: an interactive, first-person 3D scene that fits in under 1.4 MB — small enough to ship on an actual floppy diskette (and it did, custom label and all). Win32, with custom model, audio, and image compressors written for the job.

C
Win32
Size coding
Compression

Source

2019–2022

HABIL — High-Altitude Balloon Imaging via LoRa

A weather balloon rig that photographs the flight and transmits the images to the ground over a LoRa radio link — Raspberry Pi, RF95 radio, and JPEG 2000 compression to survive the tiny bandwidth. These four photos came down by radio, not on an SD card:

C
Raspberry Pi
LoRa
Embedded

Source

Jeanie reservation system calendar interface

2019–presentIn production

Jeanie — Research Appointment Scheduling

Appointment booking system built for a research lab at Texas Tech University, in production use for two years. Time-slot management, blocked dates, daily limits, automated confirmation and reminder emails, calendar export (Google/Apple/Outlook), and a full admin panel. Open-sourced under MIT.

ASP.NET MVC
C#
SendGrid

Source

E-ink display in a picture frame showing Japanese kanji from WaniKani

2023

WaniKani Carousel

A picture frame that teaches Japanese: a Raspberry Pi drives an e‑ink display cycling through the newest kanji, radicals, and vocabulary from the WaniKani API. A .NET web app renders each card; a headless browser screenshots it for the e-paper panel.

.NET Core
Raspberry Pi
E-ink
Python

Source

2026Taped out

Happy Hop — A Smiley Face in Silicon

An actual ASIC, submitted to the Tiny Tapeout GF26a shuttle: a bouncing smiley face rendered live to VGA from a 1×1 tile of custom logic. It blinks every couple of seconds and its eyes track the direction of motion. Verified with cocotb testbenches and an FPGA build before tapeout.

Verilog
ASIC
Tiny Tapeout
VGA

Source Silicon layout viewer

02 More Builds

Twenty years of side projects — software, hardware, and the space in between.

Unreal "Deja-Vu" Deathmatch Map 1998

Spent months learning UnrealEd as a kid and entered a national best-deathmatch-level contest for the original Unreal — and took the grand prize at age 11.

UnrealEd
Level design

The story, recovered

Hacking the Moon 2013

Gutted an Uncle Milton "Moon In My Room" toy and rebuilt it around a hand-soldered Hackduino with a battery-backed real-time clock, so it displays the actual current lunar phase — automatically, forever.

Arduino
DS1307 RTC
Perfboard

Build log, recovered

Perfect Park 2011

An Arduino-powered parking sonar, built as a Christmas present after watching my dad inch a brand-new SUV into the garage with a human spotter. Tells you exactly when to stop.

Arduino
Ultrasonic sensor

Propulsion Physics 2019

A Unity tool for propelling 2D/3D rigidbodies along a trajectory to a target — solve-the-launch-vector physics, packaged for easy drop-in use.

Unity
C#
Physics

Source

vsgwx 2022

A cross-platform C++17 library integrating VulkanSceneGraph rendering into wxWidgets applications, for Windows and Linux.

C++17
Vulkan
wxWidgets

Source

Bird of the Day

A daily dose of birds: one featured bird, every day.

ThinkPDF & ThinkGFX

A pair of document and graphics tools from the "Think" family of projects.

Tools

Remote Work

A 3D first-person puzzle game I'm building with my brother under our studio, Polycrime. Coming to Steam and Xbox.

Game
Unity
Steam
Xbox

Xmas Quest

A holiday adventure built for the season.

Game

Kitty Pizza: The Game 2012

A browser game where you "face your greatest enemy and take back what is rightfully yours" across a world of great pizza and geometrically simple animals. Recovered from the lost blog.

JavaScript
Browser game

Gunpowder — BDD for Unity 2012

A JavaScript behavior-driven testing framework for Unity, styled after Jasmine — bringing describe/it specs to game code.

Unity
Testing

Honorable mentions

The Wishing Well (2009) — a novelty iPhone app: make a wish anywhere, no pocket change required. Got a video review from The App Podcast.
GeoVerse (2011) — an iOS app for "dropping" Bible verses at real-world locations. Let's verse the earth.
GTIN — a mobile product-lookup website built for Palm Pilot browsers, back when "mobile web" meant a Palm Pilot.
Stock Orb Ticker — an ambient orb that glows with the market.
Sprinkler on Demand — text a message, water the lawn. SMS-controlled irrigation.
MakerBot Cupcake CNC (2011) — built one of the last Cupcake kits ever sold, then wrote a guide for making it Bluetooth-enabled that was featured on MakerBot's official blog.
KidAppReviews.com (2009–2010) — a video review site for kids' iPhone apps; got paid to demonstrate apps and show how they worked, until running it stopped being fun. Archived.
n64.social (2021) — founded and ran a Mastodon instance for the Nintendo 64 homebrew community. Archived.
way — a Ruby gem for finding partials in Rails apps, still on RubyGems with 33,000+ downloads.

03 Client & Contract Work

A selection of professional work, from early-web Flash to offline-first PWAs.

ModCloth — First Mobile Shop

Created ModCloth's first mobile shopping website — bringing the Shop to phones just as the retailer's mobile traffic was exploding (it would soon pass 50% of all visits).
- E-commerce
- Mobile web
Design Tech — Master Control Rewrite

Rewrote the company's master control program from the ground up, dramatically improving throughput and reliability of their core operations.
- Systems
- Rewrite
Design Tech — Offline-First Construction PWA

Built a progressive web app for construction managers that keeps working with no connectivity on job sites — full offline use with sync when a signal returns.
- PWA
- Offline-first
MissionMakr

All-in-one platform for organizing church short-term mission trips: trip promotion, online applications, fundraising and donation tracking, team prep, and from-the-field blogging. Launched on Ruby on Rails; the platform served churches for over a decade.
- Ruby on Rails
- SaaS
Log-a-Tour — Cranbrook

A tour-logging application built for Cranbrook.
- Web app
CL Bryant Website

My first Flash website — full-motion, full-sound, very 2000s, and the client loved it.
- Flash
- Web design

04 From the Lost Archives

I kept a blog from 2008 to 2016. The site is long gone, but the Internet Archive's Wayback Machine preserved most of it — here are some favorites, exactly as they were.

Hacking the Moon In My Room Jan 2013
Rebuilding a kids' moon-phase toy around a homemade Arduino and a real-time clock.
Test RubyMotion Apps Using Cucumber Jun 2012
A testing tutorial that found an audience — Frank + Cucumber for iOS apps written in Ruby.
Bluetooth MakerBot Feb 2011
Cutting the cord on a MakerBot Cupcake CNC — written up for the official MakerBot wiki.
Unreal Aug 2010
The story of "Deja-Vu" — the deathmatch map that won a national contest when I was 11.
The blog, as it looked in 2013 2008–2016
The whole thing, frozen in amber courtesy of the Wayback Machine.

05 Say Hello

I'm currently open to new opportunities. If you'd like to talk about software, hardware, retro consoles, or work — my inbox is open.

caleb@imap.cc

Hi, I'm Caleb Cohoon.I build things that ship.

01 Featured Projects

UltraEd — Nintendo 64 Game Engine & Level Editor

S.A.D — A GPS Speed Awareness Device

fragment — A World on a Floppy Disk

HABIL — High-Altitude Balloon Imaging via LoRa

Jeanie — Research Appointment Scheduling

WaniKani Carousel

Happy Hop — A Smiley Face in Silicon

02 More Builds

Unreal "Deja-Vu" Deathmatch Map 1998

Hacking the Moon 2013

Perfect Park 2011

Propulsion Physics 2019

vsgwx 2022

Bird of the Day

ThinkPDF & ThinkGFX

Remote Work

Xmas Quest

Kitty Pizza: The Game 2012

Gunpowder — BDD for Unity 2012

Honorable mentions

03 Client & Contract Work

ModCloth — First Mobile Shop

Design Tech — Master Control Rewrite

Design Tech — Offline-First Construction PWA

MissionMakr

Log-a-Tour — Cranbrook

CL Bryant Website

04 From the Lost Archives

05 Say Hello

Hi, I'm Caleb Cohoon.
I build things that ship.