During the Codemotion Rome 2019 conference, Jarek Ratajski delivered the talk “Lambda Core – hardcore”. We asked Jarek these questions: how important is it for developers to work on projects which are enjoyable or fun? Which mathematical skills should developers have? Any recommended reading to start a journey in the Math Land? Just like Batman, you do Java during the day and Scala at night. Why do you love Scala? Do you code differently for enterprises, compared to the coding you do for fun or for communities?