Ever since I watched @matthiasott talk at CSS Day, I've been eager to experiment with the clever tan(atan2()) technique.
So, I played around with animation durations relative to the viewport.

https://9elements.com/blog/speed-vs-duration-a-use-case-for-mixed-unit-division/

Speed vs. Duration - A use case for mixed unit division - 9elements

Animating elements in CSS can be challenging, especially when you want to ensure smooth transitions across different screen sizes. One issue that I stumble upon quite often is the inability to divide two length values in CSS. For example, calc(100vw...

9elements
No time to read? Here's the final Codepen:
https://codepen.io/enbee81/pen/xxNzJem
Bird with controlled speed

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@nilsbinder 😍 I love it! Speed instead of duration. Ha!