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Chatbot

Four chat models, each running as one brainfuck program. Ask one a question: brnfck-smollm2-135m, brnfck-qwen2.5-0.5b, brnfck-qwen2.5-1.5b or brnfck-qwen3.5-0.8b. Or show a picture to brnfck-qwen3.5-0.8b-vision and ask about it.

• ChatbotAsk a question to a chat model that runs as one brainfuck program.

Learn

What you read, in order. It starts on the first page of this list and ends in the program itself.

• Start hereWhere learning starts, and a machine to try the eight commands on.
• Brainfuck basicsThe language in ten short lessons, for complete beginners.
• Build toward a chatbotEleven lessons in which you build the tricks of a chat program yourself.
• Code patternsThe idioms of the language, each with a stepper and its cost.
• ReferenceThe language stated exactly, dialects, history, notable programs, a glossary, with sources.

Brainfuck basics

1. The machine
2. Moving
3. Numbers are letters
4. Loops
5. Building numbers
6. Reading input
7. Moving and copying
8. Making a decision
9. A small program
10. Reading brainfuck

Build toward a chatbot

1. The machine
2. Moving and copying
3. Multiplying by a fixed number
4. Obstacle 1: only one question
5. The way through: peeling off bits
6. Obstacle 2: two numbers from the tape
7. Obstacle 3: no addresses
8. Obstacle 4: size
9. One number of the model
10. Looking back
11. Choosing the word

Insights

How a question becomes an answer, part by part, and every character of the programs.

• How it worksOne question followed from your keyboard to the first printed word. No programming needed.
• Inside the programA walk through each of the four programs, with measurements.
• Program mapEvery character of a program on one map: zoom from the whole of it down to single commands.
• Compare the modelsThe four programs side by side, and the memory of Qwen3.5-0.8B: a table per head that fades and is written over, recorded word piece by word piece. Then ask Qwen3.5-0.8B yourself and watch that memory live: the model in floating point with its DeltaNet layers in whole numbers, close to brnfck-qwen3.5-0.8b but not what it computes.
• Compiled to WebAssemblyA film of brnfck-qwen2.5-1.5b answering in the browser, the same file against a brainfuck interpreter in C, and why it needs 64-bit memory.

Lab

What else the programs can do.

• Trained in brainfuckThree brainfuck programs that train a neural network themselves, from random weights, on a list of names, and print a second program that makes up new names. Train one in your browser, watch the loss fall and the weights form, see the program to scale and where its attention looks.
• Looking at a picturebrnfck-qwen3.5-0.8b-vision: one brainfuck program that reads a picture and a question. Where every square of the picture looks, layer by layer, and what the program said about four photos.
• Brainfuck that writes brainfuckbrnfck-qwen2.5-coder-0.5b: a brainfuck program that answers a task in words with a brainfuck program of its own. What it wrote for the 51 challenges and 60 blind tasks, every answer run on its test cases, how its model was taught and where it goes wrong.

Play

What you do with the language: write and solve. Each page stands by itself.

• PlaygroundWrite a program, run it and step through it.
• ChallengesExercises and puzzles with automatic checking.

About

• About the projectThe four programs side by side, the map, how it was built, limitations and sources.
• Questions and caveatsWhat "pure" means and does not mean, how it was checked, the numbers.
• Run it yourselfWhat you need to build, run and check a program on your own computer.
• CreditsThe models and the other work this project rests on, with their licences.