Dichotomous Detective v1.4

Why this project?

After 9 projects focused on canvas-based math visualizations with audio, I needed to break the pattern completely. Research into educational tools uncovered dichotomous keys — the binary decision trees biologists use to identify species. These are fundamental classification tools used in field guides worldwide, yet most implementations are static text or require expensive software like Lucid Keys. Meanwhile, games like Akinator and 20 Questions use similar algorithms but hide the mechanics behind magic. This project makes the algorithm transparent and lets you build your own classification systems.

What is it?

Dichotomous Detective is an interactive identification game where you think of an item and answer yes/no questions to help the system narrow down what it is. It uses information theory (specifically entropy and information gain) to ask the most efficient questions — each one splitting the remaining candidates as evenly as possible. You can play pre-built games about animals, programming languages, or elements, or create your own custom classification games.

How does it work?

• Data model: Each game defines a set of items, where each item has a collection of boolean properties (e.g., "Is a mammal", "Can fly").
• Question selection: At each step, the algorithm calculates the Shannon entropy for every property against the current candidate pool. The property with the highest information gain (closest to 50/50 split) becomes the next question.
• Candidate elimination: Your yes/no answer filters the pool. Items not matching your answer are eliminated visually.
• Termination: The game ends when only one candidate remains (identified!) or no more useful questions exist.
• Custom games: Users define properties and items in the editor. Games are saved to localStorage for persistence.

How to use it

• Play: Click a game card in the gallery, then answer yes/no questions. Watch candidates get eliminated as you narrow down.
• New Game: Click "↻ New Game" to restart with the same set of items.
• Create: Switch to the Create tab. Add a game name, define properties (characteristics), add items with emojis and names, then toggle which properties each item has. Click Save to store your custom game.
• Delete: Custom games have a delete button (🗑) on their gallery card. Built-in games cannot be deleted.
• Info: Click the ⓘ button in the top bar to open this help modal. Press Escape or click the backdrop to close it.