Encode secret messages with a letter shift, then automatically crack them using frequency analysis.

Build a cellular automaton from scratch: create a grid, apply the rules of life, and watch patterns evolve.

Build a tool that analyses any paragraph of text and produces word counts, frequency maps, and a readability score.

Implement a lossless compression algorithm: encode repeated characters as a count+char pair, then decode back and verify.

Build an in-memory personal finance tracker: record transactions, calculate balances, and generate a formatted statement.