Being a designer, I was always frustrated to see the boxy old-style UI on most non-stock simple calculators. Ones that had good UI (at least back in 2017) had annoying ads.
Subtle not only delivers a minimal, no-ad calculation experience but innovates, experiments & stretches the limits of usability. Furthermore, I see it as the start of my product conversation with the users at large.
If you are interested in the ‘making of Subtle’ journey give this a look: https://bootcamp.uxdesign.cc/how-i-designed-published-subtle-a-gorgeous-calculator-3f482d11a80a
– Raunaq Shah