Dachenko11: Does anyone know the algorithm for how flash sales are chosen? I have spent the entire day checking this sale, but Stacking and Jade Empire still haven't shown up. I have been going crazy since they have only shown up when I wasn't here, so I just want to know when they will show up, to have some peace at mind.
They appear to be in completely random order chosen from the pool of all games available to the flash sales (around 200 or so). Other than that we don't really know much. It appears that some games come up more than others but that could simply be within the randomness also and we'd never know. In past promos like the Insomnia sales such random picks seemed to iterate through the entire list of all total games with each game coming up within a "round" before the next round started which went through each game exactly once also. WIth this sale it seems more random than that, like each game is chosen totally at random whether or not all games have appeared once or not. There have even been a few games show up as a new flash sale item coming into the sale while the same game is already in the flash sale which supports this theory. :)
Another possibility is that some of the games are scheduled to only show up on certain days in the flash sale but not on others, or that some games are scheduled to show up 10 times and others 15 or 20 times. There is no real way to figure that out though without a lot of observation and statistical analysis over a long period of time. Plus they can change it up at any point or tweak the algorithm also.
Only GOG knows the exact algorithm although it appears pseudorandom with oddities so far. :)