Drowned neo-gothic towers twigl shader by Claude Fable 5.1, same prompt as for earlier models

Summary
This video, shared by Ethan Mollick (@emollick), showcases a real-time GLSL shader generated by Anthropic’s Claude Fable 5.1 using his benchmark prompt for “drowned neo-gothic towers.” The resulting Twigl shader program renders a stormy, low-poly procedural sea submerging illuminated Gothic spires under falling rain and lightning.

What is shown

• [00:00 - 00:04]: A dark, raymarched ocean scene with rolling swells, rain streaks, and dark silhouettes of Gothic spires with lit windows poking above the water under a moonlit sky.
• [00:05 - 00:07]: Flashes of lightning illuminate the overcast clouds and sharp spire architecture on the left horizon.
• [00:08 - 00:12]: Ongoing dynamic wave motion and rain particles, with another lightning flash visible in the stormy sky around [00:10].

Claims & numbers

• None (silent screen capture recording of a shader execution without narration or text overlays).

Notable quotes

• None.

Assessment
This is a screen recording demonstrating the code generation capabilities of Claude Fable 5.1 executing a single-pass WebGL/Twigl fragment shader. The animation is rendered purely via procedural math and code without post-processing or video diffusion generation.

Lyrics & themes

• Silent / no audio or lyrics. The visual theme explores a moody, gothic cataclysm, depicting forgotten grand architecture slowly swallowed by turbulent ocean waters.

Lore & references

• Mollick’s Twigl Benchmark: Ethan Mollick frequently evaluates the coding and spatial reasoning of successive frontier LLMs by asking them to write complex, compact GLSL shaders (such as “drowned neo-gothic towers” in Twigl format) without external assets.
• Progressive Model Benchmarking: Comparing how new models (like Claude Fable 5.1) handle volumetric lighting, raymarching, reflections, dynamic fluid movement, and particle effects directly in code compared to earlier generations.

Visual style & craft

• Render Style: A compact procedural GLSL/Twigl fragment shader running in real time.
• Craft: Features signed distance functions (SDFs) and raymarching for the architectural spires, sinusoidal/procedural heightmaps for the water waves, dynamic alpha-blended rain streaks, emissive window lighting, and timed sky flashes simulating lightning. A desktop mouse pointer briefly appears on screen, indicating a live screen recording of a browser window.

Described by gemini-3.8-flash on 2026-10-08 from the video’s audio and frames.