Everything is logic and math, therefore a computer is the most fundamental machine because its purpose regards performing all logic/math operations from the simplest up to the most complex it can physically represent. Despite this somewhat philosophical sentence, I'm usually working with open source, Linux and C. As an additional experience, I'm also working with C#, .NET Core framework, and ECMAScript (a.k.a. javascript) for developing web applications for a company (I would like to use C, though :-) ).