Good job. Simpler than I imagined.

There's also Sun Surveyor https://www.sunsurveyor.com/ which let's you visualize where the sun is at any time of day and year in 3d with your phone (the camera overlay feature is called LiveView). I've used it for similar things a few times. It's my favorite app, though least used.

I use ‘Sun Tracker’. Also similar. Maybe missing some features, but free.

Edit: I see now it has paid premium features. I only use the basic ones (not very often)

Kind of like a DIY Project Sunroof: https://sunroof.withgoogle.com/

Sketchup (free version) also lets you visualize the sun shadows based on location, date, and time. But it's not showing the strength of the sun like this.