Eternalfest is a modded version of the Flash platformer game The Caverns of Hammerfest. Access to to play the mod is restricted currently (private use) because we are not sure about copyright issues. You can see videos the project's Youtube channel. I am leading this project in a group of about ten people and 2-3 other developers (it varied other time since the beginning in 2013).
This is a relatively large project that helped me to acquire a lot of experience: software architecture, database administration, security, server management, reverse engineering, interpreters, APIs design, web scrapping, containers, continuous deployment, front-end technologies, backward compatibility and team management.
The Eternalfest website allows you to create backups of your account on the original game: the idea is to be able to transfer your progress. The game engine is a rewrite of the original engine in Haxe. We have graphical level editors and bundlers (to assemble multiple levels in a single game) in Java. The private part of the website allows users to easily share their games so they are immediately available, to support it it also contains a file hosting service. There is a development framework to easily patch the engine: it allowed some game creators to do some impressive levels. A lot of work was also put to ensure backward compatibility: games created with the format used in 2013 are still working today. I wrote my own Flash decompiler (with other Flash tools) in the context of this project.