Tree Appreciator

Tree Appreciator is a slow spot-the-difference game with a twist: the two trees are grown procedurally from a seed, so every round is a fresh pair. Each tree is a 3D model rendered with Three.js, and the differences are small, physical things — a missing bough, a visiting bird, a branch that turns early. You tap a difference in either tree to notice it, drag to orbit the pair, zoom in to inspect the branches, and spend limited hints when a difference refuses to show itself. Completing a pair earns appreciation points, leaves and herbarium entries, which gives the game a gentle collection loop instead of a fail state.

The pace is the point. There is no timer, no leaderboard and nothing to lose, so the game works as a five-minute pause rather than a competition. The trees are beautiful in a quiet way, the camera lets you look at them from any angle, and the differences are designed to reward close looking rather than pixel hunting. Music, animation and achievements were added by the model without being asked for in detail, according to the developer, and they are what turn a technical demo into something that feels like a small product.

The build story is one of the cleanest examples of AI-assisted game development this month. Simon Willison made Tree Appreciator with a single prompt to Claude Opus 5.5 Max in the default Claude iPhone app — chat mode, not Claude Code. The prompt asked for a Three.js game called Tree Appreciator that shows two algorithmically generated trees and makes the mechanic about appreciating the differences between them, with the instruction to “think hard about how to make sure it is both fun and beautiful.” Claude worked for 3 hours and 7 minutes before returning the game, complete with music, animation and achievements.

It is free, runs in any modern browser, and works on desktop and mobile. Willison noted that telling the model to make sure the game is fun worked “uncomfortably well” — a useful data point for anyone who thinks prompt quality is mostly about technical specification. If you want a calm, unusual browser game, or a case study in what a single well-written prompt can produce, Tree Appreciator is worth a tab.