Exhibit No. 013 · Animation

Drowned gothic city shader

Ethan Mollick’s favourite test: an endless city of neo-gothic towers half-sunk in a stormy sea, drawn entirely by a shader.

Prompt

> create a visually interesting shader that can run in twigl-dot-app make it like an infinite city of neo-gothic towers partially drowned in a stormy ocean with large waves. Output a single self-contained HTML file that runs the shader full-screen with WebGL.

What it tests

Procedural graphics with no assets at all: raymarched shapes, waves, fog and lighting, where quality differences show at a glance.

Origin

Ethan Mollick · 2025

2.2M views on the original post

Prompt wording adapted from the original.

Difficulty

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Results

Claude Opus 5.5

Run on 2026-10-19Open the raw answer

Second attempt. The first answer had a bug and was taken down; the same prompt was answered again from scratch, planned more carefully and read through before submitting. The shader is written for twigl’s “classic (300 es)” mode. Drag to look around.

Test conditions

One attempt per test, with no edits after running. Where a first attempt didn’t work, the test was answered once more and the exhibit says so; answers that still don’t work are not shown. Run inside a Claude Code agent session, which includes its own system prompt, rather than the raw API.

All results for Claude Opus 5.5

Save the answer as a .html file and open it in a browser to compare it with the one above.

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