Invent a one-screen browser toy

Create a one-screen browser toy around this surprising rule: [RULE]. It should invite curiosity in under five seconds, respond to at least three different user actions and reveal one delightful but understandable consequence. Keep the interaction short enough to replay.

Before writing code, define the rules, win or discovery state, accessibility alternative and how to reset. Implement a working HTML/CSS/JavaScript prototype with no build step. Make it responsive, touch-friendly and keyboard-operable. Use original shapes, words and sounds only; do not borrow a named game's characters or branding. Include a no-audio mode, reduced-motion mode and a visible explanation of what data stays on the device.

Return the source files and a human test checklist covering mobile, keyboard, focus, reset and one intentionally confusing action. Do not call it playable until the code actually runs.