>>15383879
They are mostly brain-dead, but they are there to overwhelm you. Also the shape and size of the "arena", weaponry you are equipped with and consumables/items found in said arena you play in (health, armor, ammo, power-ups, vehicles in the case of II) matter a lot when it comes to the fight, it's not just about the enemies you are fighting against and their numbers. Forgot to say the fact that you aren't seeing the whole fight as you play as in you do in a sidescroller, sometimes you have to predict when an enemy that was behind you or just out of your FOV is going to attack you to avoid getting damaged (example, kleers running behind you, if you want to play in the hardest settings you better learn to avoid them without seeing them by just listening).
A thing you have to take account in is the fact that some enemies, like the giant spiders in Serious Sam II, don't have such brain-dead shooting patterns, as they actually calculate where you are going to be if you keep moving at the same direction when they shoot their projectile attack, meaning you need to change direction just as it shoots you to not get hit. Also when you add a 3rd axis shit gets finicky with air enemies and their homing projectiles that have to be shot in order for them to not hit you (Serious Sam II helicopters). Some of these "shootable" projectiles don't home however, and are reserved to the lesser kind of enemies, like the rockets shot by the stationary turrets and the literal red bull looking guys (they are not "shootable" if they are the giant mini-boss variant, though).
You can't deny that this game takes a good amount of precision, reflexes and coordination that makes it feel almost bullethell/SHMUP-like to some extent, reason I thought this game could be liked or popular to some extent amongst japanese players, even if it's a fringe/niche small group of players.