I once made a rather ghastly simulation of particles flowing under gravity using the Java-based Agentsheets program.
Now the state of the art has moved ahead significantly.
Today’s invention is a watch which is a simulated egg-timer. The program involved would show an hourglass on-screen through which would flow simulated particles.
This could be calibrated to provide per-minute timings and would operate effectively and accurately -independent of the orientation of the watch itself.
For fun, it could be made with user-settable parameters eg particle size and ‘g’ (as well as having visible particles of ‘air’ flow upwards as the ‘sand’ flowed downwards).