How GPT5.6 Sol Ultra FAILED my digital twin Hourglass test

Continuing my benchmarking of how well AI can build a digital twin of an hourglass timer - this time with GPT5.6 Sol Ultra mode. Compared to Claude Fable 5 and Opus 4.8, sadly GPT 5.6 lags behind. GPT5.6 took 25 minutes to build it, the end result still looked like the output I'd get from GPT3/4 days.

I use this standard prompt for all my tests: Build me a single page application that is a digital twin of an hour glass timer. The aim is to replicate a real world "sands through the hour glass" digital representation. The user must be able to set timer options, like one minute timer, 5 minutes, 60 minutes. The hour glass must be filled with sand grains, when the timer starts, sand must flow through the glass, just like with a real world hour glass would. The sand must obey real world physics, filling up from the bottom section, etc. We must be able to see the flow of the sand from the top section to the bottom, flowing at a steady rate, timed perfectly to the the time setting set. Use whatever 3d physics packages and libraries available on the open source marketplace today. I tried a second time to nudge GPT5.6 to improve, but sadly ran out of quotas. I was quite disappointed, didn't bother pushing the code to github. Even with its second attempt, GPT 4.6 was still anchored on basic animation, simple physics, no flip the hourglass, no sound effects. This after spending some time doing the research, in the same way Opus and Fable did, but somehow landed on something quite different. When I get my credits back, I might just feed it Fable's codebase and research, and get it to write a critique about where it got things wrong!

Here's what GPT5.6 Sol Ultra produced:

Compare this with Fable 5: