A part or stage in a game that escalates in difficulty in a very short
period of time, separating the casuals from the actual gamers.
Not to be confused with a steep/vertical learning curve, as these mean that the game is
hard to learn and master from the beginning.
Games with a casual filter
will give you a false feeling of confidence as the filter comes after you have learned the basics and started progressing, just to catch you off guard and make your run end, usually having to start from zero again.
Some examples of casual filters in games include the winter in Project Zomboid and your first
goblin raid in Dwarf Fortress
Person 1: Ayo wtf is this I just lost my 30h
run, how do you even survive the
winter?
Person 2: Welcome to the
casual filter, play more and git gud