Barry_Woodward: GOG Twitch Streamer Pieman said on June 10th (https://www.twitch.tv/gogcom/v/71675601?t=01h49m53s), "By doing different things, by either buying games or by doing specific events, like going to the GOG.com Twitter or by coming back next Thursday, I believe, for when we're going to have a little thing going down, you'll have the chance to unlock EXP points that you can then use to buy games."

Also, SCPM discovered a whole host of games in the pipeline (https://www.gog.com/forum/general/games_that_are_unofficially_confirmed_for_release_in_the_future_part_2/post3811), some of which have already released during this sale. Could the "little thing going down" today involve multiple releases from the list?

ElTerprise: See. We need them - but granted the abbreviation id for InDev titles is dumb xD
I guess it's similar to other sandbox games like Minecraft / Terraria / etc.... but i'm not sure. I think they offered a demo on the official site though...