If you’re looking for how Flatten works, check this article.
How it all started
In Digimon World, you could inflict an LCD status effect on an enemy Digimon called “Flat”. It reduced their 3D model to a DOT sprite like in the v-pets and caused them to use a weak attack. It seems pretty appropriate to include for any 3D Digimon game that wants to include DOT sprites as with set Bit Depth. At the time, I already had this mechanic planned but no theming. So reducing the opponent’s dimensions one by one until they pop out of existence made a lot of sense. Originally, the balance was centered around having to obtain 4 instances of flatten. This didn’t test well. It took far too long to 4-hit-KO even when it can pierce evolutions. The next step was to tweak that number until it felt right in many many games. There was one point where I was torn between requiring 3 flattens and a regular damage hit versus 4 flattens and I ended up just including both due to how supports could be used to add more flats. The 3 flats with damage requirement was slightly too powerful while 4 as a fixed amount was way too slow without a constant supply of support-based flatten. Full Article