Very nice. But a few issues.

1. The incorrect messages disappears too quickly. And it appears slightly off the screen (I am on a MBP 15"). It should persist.

2. There is no zoom for Europe. I tried using Mediterranean. So when asked to show Estonia, I can't even get to the NW European states without scrolling. Which means that the incorrect message will never be seen.

Similarly, asked for Guernsey had to zoom in but it selected Jersey. No amount of zooming will let me select from the two. It becomes grainy.

Thank you for your feedback!

You should be able to pan the map as well, so you may get to Estonia after all ;)

Definitely forgot that not everyone has large laptop screens though, absolutely fair.

How much does the syntax differ from ruby ?

Do you think I should learn crystal by porting a smallish ruby CLI app to it, or make one from scratch porting a small bash app ?

I was thinking of doing it in `go` or `rust` but thinking of crystal after seeing this article.

Can anyone make recommendations for Astrophysics ?

An Introduction to Modern Astrophysics by Carroll & Ostlie is the Bible, but it is quite large physically and in scope and better serves as a reference for most people.

For various topics, I would look at:

Introduction to Cosmology by Ryden for cosmology at the undergraduate level.

Cosmology by Weinberg.

The Exoplanet Handbook by Perryman.

An Introduction to Modern Stellar Astrophysics by Carroll & Ostlie.

Particle Astrophysics by Perkins.

Modern Statistical Methods for Astronomy by Feigelson.

Statistics, Data Mining, and Machine Learning in Astronomy by Ivezic.

I can post more in other topics if anyone is interested.

Admittedly more of an Astronomy text book but a great starting point is Universe by Freedman and Kaufmann.

https://www.goodreads.com/book/show/705558.Universe

I remember Carroll's Modern Astrophysics being very good. It's quantitative, so it helps to have some physics background.