We are mainly using an open source game development platform GDevelop. One of it’s main strengths is on making quick prototypes and continue on to develop from there to full stand alone release. You can create your games to multiple different platforms with ease: Windows, MacOSX, Linux, Android and even on iOS. Also web server launchable HTML5 versions are possible.
The secret of GDevelop lies in it’s ability to be learned quickly, with ease and you can start creating games and having results quite fast.