if you click on "Cultris II" on this web page,you can see its page and the screenshots. One screenshot shows a player on the online-mode who is about to create a new room. Instead the two game modes,"Standard" and "Swiss Cheese" that you can select on the latest version there,here are four modes. "Standard","Swiss Cheese","Survivor" and "Speed". It is very simple to find out that the game mode "Survivor" has (ONLY for online play!) been replaced with the challenge "Survivor". But what was the game mode "Speed",how it worked and why it got deleted?
speed mode: the slowest player gets lines, i think those grey lines were also un-clearable.
no one really used it, so it got deleted.
i would love to play that mode, sounds really cool and surely it is a good speed training :)