Neural network

Build the real thing

Perceptron: knobs = weights, LEDs = outputs

Build a perceptron you can touch: three inputs, a knob for each weight, a sum, and an LED that lights when the total passes a threshold. Turn the knobs until it gets the answers right; that's training, done by hand.

Cost

$ · Under $25

Time

A few sessions

Screens

No screen needed

Build it in bricks

139 pieces · 18 steps · Easy · parts checked September 24, 2026

Booklet: Activities Pass members now · free for email subscribers from November 12, 2026

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Where to buy the parts

The parts lists are free. Booklet: Activities Pass members now · free for email subscribers from November 12, 2026.

Do this on a computer: you save a file here, then upload it to the store.

1. BrickLink: Wanted List (XML)

   Open the file in a text editor and copy all of it. On BrickLink, choose Want → Upload → BrickLink XML format, paste, verify the items, then add them to a Wanted List.

2. LEGO Pick a Brick: Parts upload (CSV)

   A US & Canada beta, and some parts may not be stocked. On Pick a Brick, choose Upload list, add this file, then Upload.

3. BrickOwl: BrickLink XML

   On BrickOwl, choose Wishlist → Import → Import BrickLink XML and upload this file.

4. Rebrickable: BrickLink XML

   Make a Part List on Rebrickable, choose Import/Delete Parts, then upload this file on the BrickLink XML tab.

Full parts list with part numbers (CSV)

Parts data: Rebrickable, checked September 24, 2026.