I think about being able to create my own achievements, basically writing a short description for it, maybe adding an icon. I should be able to mark them as done/not (yet) done myself and they should be clearly marked as custom achievements and separated from official ones.

Also I would love to have some kind of gog online place where you can share your custom achievements for any game, creating lists and vote them up so you can easily find popular ones and integrate them with one click. This way you can find some new challenges for a game and even share them with your friends easily.

There are multiple ways of having fun with such a feature:

1) You already completed a game with all achievements but search for more ways of playing the game.

2) The platform you're playing the game on doesn't support achievements although the game itself got achievements on other platforms. So just add those official achievements as custom ones yourself. That way you don't need to feel like you're missing out on some parts of a game just because you bought it on another platform.

3) The game only supports ingame achievements but not the platform. Just transcribe those achievements into galaxy yourself.

4) The game doesn't contain any achievements at all but you wanna share your progress (or like point 1, find new ways to play it). Especially nice for older games and at this point I want to mention http://retroachievements.org/, providing achievements for playing older games on emulators. Being able to create custom achievements, you could integrate those easily.

5) You can adjust your achievements to your needs. Maybe you are speedrunning a game and would love some achievements for doing certain stuff in a short time or performing some glitches or tricks. Or maybe you found an interesting challenge on Youtube and loved it so much you did it yourself and now wanna show it. You completed a Super Mario game without collecting a single coin? Mark it as an achievement for yourself.

Of course people could abuse that system and just mark stuff they didn't do. But I see custom achievements not primarily as a way to brag off about what I did achieve but more about sharing how I spent my time and how much I enjoy a game and what ways you can also play it.

Galaxy 2.0 is in an early stage and maybe this is a feature better to implement later when more important stuff is completed already. I just wanted to share this idea as I think it is an awesome way of expanding your game experience.

Sorry for the necrobump, but I just wanted to say that this is exactly what I am looking for as well; support for cheevo-less games and new fun additions for the rest.

Seeing the title I was ready to say "Can't be done, developers have to manually code every achievement" but then I saw that you are talking about self-assigned achievements that you tick yourself manually. Yeah that would work and would be fun, but it'd need a big infrastructure: A way to submit custom achievements and have the community vote on good ones to show in Galaxy and report troll/racist "Eat 9 watermelons" etc/porn achievement images etc, which would take manpower from GOG. It's unlikely that GOG would create this feature because of the work it would require from them to maintain it and keep it clean and safe.

If they do create it, they would probably tie the conditions to something they can punish bad people with, such as "You must have spent at least $10 in the store, and if you upload racist/porn/troll images and achievements, we ban your account and you lose all your games." That would work and would cut down on the moderation manpower requirements.

There may actually already be a gaming community website somewhere that already has "custom achievements" the way you describe. Sounds like something game fans would create.