Crystal is a language with a focus on developer happiness, like Ruby. The syntax and OOP model resemble that and any Ruby developer feels right at home.
It's statically typed and compiles to native code, making it intrinsically type safe and blazingly fast. Built-in type inference makes most type annotations unnecessary, resulting in easy to read and clean code.
It can be a good asset for performance-critical applications and is very approachable for Rubyists
Crystal is a joy to work with and having it in your toolbox is an asset, even when writing Ruby code.