Must confess, I don't know for sure but probably a highly portable language such as Java.
Java works by compiling your source code into something known as bytecode. You then have a bytecode interpreter for every platform the language supports, and run it from there.
In that way, your source code can be platform-agnostic.
Java bytecode is well-defined, with its own instruction set and syntax:https://en.wikipedia...i/Java_bytecode
Python is up and coming, it is a scripting language (what we used to call an interpreted language). Some Linux utilities (for example, the system cleaner BleachBit (which you can think of as being a kind of Linux equivalent of Ccleaner)) is actually a Python script.
It is a very full-featured language that is gaining popularity and use, especially in RPi environments.
There is still some call for C, bit it has been largely superseded by C++ and c#.
Many one-player games need to run on various platforms nowadays, from desktop PCs through to tablets as well as online.
The number of platforms (hardware and software) that must be supported is growing all the time.
My current favourite time-waster is 2048