Gosu for C++
Gosu is written in C++ 2003 with minimal dependencies (no boost), and will slowly be updated to C++ 2011/2014.
You can check out the Travis CI configuration to see which compilers and OS versions still work.
The Windows version of Gosu is available for download on GitHub and compatible with the latest version of Visual C++. On other platforms, you can use Xcode, CMake, or make and pkg-config to build Gosu games.
Installation is especially easy on macOS with Homebrew: brew install libgosu
C++ Project Structure
The wiki has platform-specific guides for setting up C++ projects.
Alternatively, you can take a look at the Gosu port of TheOm3ga’s FreeGemas.
The port is unfinished and rough, but the project can be built for Linux and macOS with CMake, and for macOS and iOS with Xcode.
Ruby/Gosu for iOS, via RubyMotion: motion-gosu
The RubyMotion version of Gosu is a work in progress port and does not support Android.
The documentation is right on the motion-gosu GitHub page, but you can also look at another example project:
Its repository is structured in a way that makes it easy to run the same code with ‘normal’ Ruby, RubyMotion for macOS and RubyMotion for iOS. (Please don’t let the unfinished gameplay and missing artwork distract you.)
A Word of Warning…
The C++ and RubyMotion versions of Gosu are not for the faint of heart. They are nowhere near as polished as Ruby/Gosu.
You’ll see terrible error messages, and you’ll need to know your tools well enough to fix them. Poking around the source code often helps, too.
Nevertheless, if you have written a great Ruby/Gosu game, porting it to RubyMotion or C++ might be the best way to share it with the world through Apple’s App Store for iOS and macOS. Please file an issue if you run into unexpected limitations.