What's the best sandbox game (or openworld games) around that's cross
platform, free, opensource and never gets boring? Is it
minecraft because it's written in Java? Is it
SimCity, Grand Theft Auto?
Well the ultimate sandbox game ever developed has to be a thing called
gcc - Gnu Complier Collection, you can build anything you want
with it. All you need is a computer with enough space to install it, a
text editor and the manual for the language binding you want to
use. You can use a number of languages with gcc such as C, C++,
Objective-C, Fortran, Java, Ada, and Go and maybe others as well.
There are no constraints in the worlds that you can create with
gcc provided you have enough time and determination. It's the
ultimate sandbox game!
If gcc is too lowlevel for you then you might want to try
something like haskell, perl, ruby or python. All of
which were probably created with gcc anyway.