What is the most minimalistic app you'd ever created?

I've been a big proponent of minimalism.
Especially when it comes down to engineering.
Especially for the software engineering.

Albert Einstein -- Everything should be made as simple as possible, but not simpler.

According to the second law of thermodynamics, in the physical world the entropy keeps increasing.
So does the complexity of our software, and we, the software engineers, are to be blamed.

I wrote about minimalistic architecture: https://dev.to/dmitryame/minimalistic-architecture-for-minimalistic-product-ffd

I even tried to invent most minimalistic social sharing platform: https://www.echowaves.com/

The most minimalistic app I've ever came up with https://www.echowaves.com/chimingclock -- it's only about 100 lines of code, 1 screen, no customizations, but I still think of it as very useful app. Of course, there is a lot of complexity that went behind the scenes building it. It took me almost a week to find the right combination of those 100 lines to make it work -- simple is not easy.

If you are as passionate about eliminating complexity in our lives (read in software we build every day), and if you've ever created something that just bare bones simple, share in comments about your experiences.