Celebrating 100... [12 HOURS LEFT]

... 100 what? Will reveal it in the first cart of my train, but if you solved my last puzzle, you might know already...

The train consists of these games:

x https://store.steampowered.com/app/230270/
# https://store.steampowered.com/app/2329470/
x https://store.steampowered.com/app/3295160/
XX https://store.steampowered.com/app/1217230/

wait, uhm, that's the wrong list... now where did I put it...