What’s the best thing about the language/environment you work in?

The Elm type checker and compiler make me happy every time I use it.

The fast iteration cycles of REPL driven development are really rewarding. I'm contributing to a REPL, and being able to rapidly test new functions inside the same environment I'm coding is a really cool experience.

CTRL R, R: Refactor rename
F12 : Goto definition
CTRL -: Go back to where I was