DEV Hacktoberfest 2026 · Week 3 · Slow and Steady
The problem
On real wearable data, people wearing Fitbits for two months, a fixed 10,000-step goal was met on … of days.
Missing your goal two days out of three is not motivation. It is how people quit. Slow Start gives you a goal you can actually win, then moves it with you.
How it works
Your phone does not know how fast it can send data, so TCP starts slowly, speeds up while things go well, and backs off when something is lost. Slow Start does the same with your steps.
Day one asks for 1,500 steps. Anyone can win that, which is the point.
Every win doubles tomorrow's goal until the first miss tells it where your level is.
After that it adds a fixed step per win, 1,500, a number chosen by testing it, not guessing. Steady, like a sloth with a plan.
Never to zero, never a lost streak. A smaller goal tomorrow, and the giant is still there.
Try the controller
This asks the real server for each goal. The controller is one of four core functions written by hand for this project; while one of them is still being written, a plain stand-in answers and the widget says so.
Days here are pretend: every button adds one day.
The second limit
TCP has two limits: how fast the sender wants to go, and how much the receiver says it can take. Slow Start has two as well. The rules above are the first. The second is TabPFN, an open tabular foundation model, which reads your last weeks and predicts a level you will reach about 7 days in 10. Your goal is the lower of the two.
We tested whether that prediction beats something simple, on held-out days it never saw. On this data, it does not: it is a tie with a plain "your own 30th percentile" rule. We say so here and in the write-up.
| Goal | Validation | Final | Asks for |
|---|
The game
Its health is your goal. Every step you log is a hit. Catch it and it follows Slumbrock home. Parks, waterfronts, streets and gyms each have their own, and somewhere new brings a rare one.
Open the field guide: where to find them, how to catch them, trivia
Made for lazy people
The goal arrives every morning. Weights and reps too, if you lift. You just walk.
No gym, no problem. An evening walk raises Slumbrock just as well. Built with parents in mind.
Tell Slumbrock you are unwell and the day is excused. Nothing is cut. Code decides that, not the model.
Log from a place you have never logged from and a rare creature turns up. Your location stays on your phone.
Gemma, an open model, reads a one-line check-in and answers as the giant. It never sets a number.
No account. Everything is saved on your device. The server processes each request and keeps nothing.
Why open