Free computer science fundamentals activities for your class

The first lesson: counting in 1s and 0s until it feels natural.

How computers think in 1s and 0s - and how you can too.

A photo as millions of numbers. Makes binary concrete right after the first lesson.

Every photo is just millions of numbers arranged in a clever way.

The same information in less space, and the idea of lossless compression.

Make files smaller without losing information - the magic of compression algorithms.

Take apart a QR code: finder patterns and error correction students can see.

Take apart a QR code to discover finder patterns and error correction.

Toggle AND, OR and NOT, compare truth tables, then build a half adder.

Toggle interactive logic gates, compare truth tables, and build a half-adder circuit. See how three simple operations create all of computing.

The switch under every gate, and why Moore's Law mattered for fifty years.

Transistors are voltage-controlled switches with no moving parts. Learn how one builds a NOT gate, why Moore's Law doubled transistor counts for 50 years, and just how small modern chips really are.

RAM, cache and storage, and why where data lives changes how fast it is.

RAM, cache, and storage - understand where your computer keeps things.

Everyday algorithms, putting steps in order, and a race between linear and binary search.

Explore everyday algorithms, order steps correctly, and race linear vs binary search to find a number.

Flowchart symbols and a decision tree, and how a flowchart maps to code.

Learn flowchart symbols, walk through an interactive decision tree, and see how flowcharts map to code.

A quick look at sorting and searching before the deeper lessons.

Watch sorting and searching algorithms in action - see why some are faster.

Race bubble, selection and merge sort, step through one comparison at a time, and see why O(n log n) wins.

Race Bubble Sort vs Selection Sort vs Merge Sort side by side, step through Bubble Sort one comparison at a time, and see why O(n log n) beats O(n^2).

Students find a path by hand first, then watch BFS and A* do it and compare how many cells each explores.

Draw walls, pour water, and watch BFS and A* race to find the shortest path. Then try it yourself.

Six ways to build a maze, each one an algorithm students can watch.

Explore 6 different maze generation algorithms.

Four rules, and the Game of Life: how simple rules produce complex behavior.

Explore Conway's Game of Life and discover how four simple rules create gliders, oscillators, and infinite complexity from a grid of cells.

Crawling, indexing and ranking: algorithms at the largest scale.

Explore the three big ideas behind every search engine: web crawlers that walk billions of pages, inverted indexes that turn queries into instant lookups, and PageRank that uses links as votes to rank the best results first.

Hello world, variables and math, if and else, and a loop that draws a pattern.

Write and run hello world, explore variables and math, make if/else decisions, and see loops create patterns.

The three building blocks of every program, in a few minutes.

Variables, conditions, and loops - the building blocks of every program.

Billions of instructions a second: a good hook for why efficiency matters.

Your computer runs billions of instructions per second. Let that sink in.

Edit a short program and watch a bot fight with it on real physics. Motivating for students who want to see code do something.

Your bot can run your code. Learn the brain commands, then play with ready-made snippets for chasing, kiting, circling, firing, and self-righting. Edit the code, press Run, and watch your bot fight a live opponent on the arena's real physics.

Train a small neural network and watch it learn a pattern.

Train a neural network and watch artificial intelligence learn patterns.

Neurons, weights and layers: adjust one neuron by hand, then watch a network train.

Explore how neurons, weights, and layers work together. Adjust weights on a single neuron, visualize a full network, and train one by watching loss decrease.

Which chart for which data, and how to spot a misleading one.

Learn when to use bar charts, line charts, pie charts, and scatter plots. Spot misleading charts and test your skills with quizzes.

Scatter plots, spurious correlations, and how one outlier moves a trend.

Build scatter plots interactively, explore spurious correlations, and toggle outliers to see how one point changes the whole trend.

Why polls get it wrong: sample size and selection bias.

Polls and surveys try to learn about a big group by asking a small one. Explore how sample size affects accuracy, how selection bias secretly distorts results, and the famous 1936 election poll that got it spectacularly wrong.

Students try to be random and fail. A short, memorable opener on patterns.

Challenge yourself to be truly random and spot fake patterns.