Apps and demos

Jeff Kastl, software engineer working in data and AI on Google Cloud. Google Cloud Certified Professional Data Engineer. GitHub · Google Cloud certifications

Part experiments, part musings: things built to learn how something works, test an idea, or scratch an itch. Most run right here in your browser.

Showing all 24 apps

• Advanced Data Engineering

  Seven advanced data engineering topics as hands-on demos: watermarks, exactly-once, CDC, Iceberg-style tables, skew, lineage.

  Data & ML
  Open app → Source

• Agent Triage Simulator

  A multi-agent service desk, simulated: a router, tool-using agents, guardrails and a human approval step, with a live trace.

  Data & ML Privacy & Security
  Open app → Source

• Data Engineering Concepts

  Nine core data engineering ideas as hands-on demos: ETL vs ELT, idempotent loads, SCDs, partitioning, DAGs and more.

  Data & ML
  Open app → Source

• Drop It on Purpose

  Why a router that refuses to drop packets ruins your video call, and the fix. Part of Tolerance.

  Sensing & Signals
  Open app → Source

• Emergence

  A field guide to complexity from simple rules: seven live simulations, from boids to sandpiles.

  Open app → Source

• Intarsia Print

  Python CLI and local web UI that turn a prompt or flat graphic into a printable multi-level relief STL. Runs on your machine, not here.

  View source →

• Knee Rehab Timer

  Offline-capable circuit timer for a knee rehab routine.

  Health On a phone
  Open app → Source

• Light Through a Finger

  How a pulse oximeter reads oxygen, what fools it, and your own pulse through the camera. Part of Tolerance.

  Sensing & Signals Health On a phone
  Open app → Source

• ML Showcase

  Machine learning step by step on simulated clinical problems: four models you train and poke, live in the browser.

  Data & ML Health
  Open app → Source

• Ride Report

  Live ride-quality meter for your phone. Lay it flat on a tray table and watch the turbulence.

  Motion & Navigation On a phone
  Open app → Source

• Scatter!

  Pass-the-phone category game: roll a letter, then name something in 10 categories before time runs out.

  Games On a phone
  Open app → Source

• Scratch the Code

  A real QR code you can deface, and the Reed–Solomon decoder that repairs it live. Part of Tolerance.

  Error Correction
  Open app → Source

• Scroll Report

  A rolling 3D seismograph of your phone's motion over the last 20 seconds.

  Motion & Navigation On a phone
  Open app → Source

• Slide Pyramid

  A six-gigapixel microscope scan that opens instantly in the browser, and the pipeline that cuts it into a training set.

  Data & ML Health
  Open app → Source

• Stain Drift

  Same tissue, three labs, three shades of pink. Unmix the stains, normalize them, and stream three days of scans past a drift monitor.

  Data & ML Health
  Open app → Source

• Tear-Proof Secrets

  Split a password across printable tags so that any three of five rebuild it, and two reveal nothing. Part of Tolerance.

  Error Correction Privacy & Security
  Open app → Source

• The Liar's Game

  Twenty questions against an opponent allowed to lie. The math that catches it is error correction with feedback. Part of Tolerance.

  Error Correction Games
  Open app → Source

• The Vote

  Majority voting, von Neumann's threshold, and why the spare on Ariane 5 failed too. Part of Tolerance.

  Error Correction
  Open app → Source

• Tolerance

  Right answers from wrong parts: the front page for six exhibits and four Lab experiments, each also listed on its own here.

  Error Correction Sensing & Signals
  Open app → Source

• Traitors, Pass-the-Phone

  A party game that runs the Byzantine Generals protocol. With three players the loyal side can't win reliably; with four it always does. Part of Tolerance.

  Error Correction Games On a phone
  Open app → Source

• Two Wrong Answers

  A Kalman filter blends noisy GPS with a drifting accelerometer, and learns the drift. Part of Tolerance.

  Sensing & Signals Motion & Navigation
  Open app → Source

• Where Am I

  GPS as circles and a bad clock, and why altitude is always the sloppiest number. Part of Tolerance.

  Sensing & Signals Motion & Navigation
  Open app → Source

• Word Flashcards

  Flashcards for beginning readers at a kindergarten (K) reading level: simple 3-letter words, by card count or timer.

  Open app → Source

• Your Phone's Fingerprint

  Factory calibration errors in your phone's motion sensors form a stable ID. See yours, entirely on your device. Part of Tolerance.

  Sensing & Signals Motion & Navigation Privacy & Security On a phone
  Open app → Source