Controlling learnability in action games
Challenges in action games can differ in learnability: how quickly the player improves through practice. First I'll show some examples of high and low learnability, and then discuss why you might want to design one or the other.
I first discovered this concept by analyzing Hollow Knight bosses and haven't had time to apply it much outside of that, so that's where my examples will come from.
Here are some high learnability bosses:
Troupe Master Grimm
These are both known for absolutely wrecking most players the first few times they face them. But because each attack follows the same pattern every time, you can use the same responses every time. Players inevitably pick up on these responses after a few tries and then it's just a matter of training muscle memory and the fights become easy.
And note that this is achieved without trial and error. Their telegraphs are designed so you can likely guess what's going to happen and how you need to dodge even if you haven't seen the attack before.
Here's a very low learnability boss:
Markoth is not a super hard boss. There's a decent chance you'll beat him on your first try. But to experienced players, he is far scarier than Mantis Lords or even Grimm. I'm at a point where I can easily beat Mantis Lords without ever being hit, but if I go and fight Markoth, I'm probably going to take at least 4 hits. Players just don't improve at Markoth as easily as they do at Mantis Lords or Grimm. Why?
Because although he has fewer attacks, his don't have repeatable counters. How you need to move to dodge his attacks depends totally on the context: your position, his position, what angle the sword is coming at, what angle his shield is at. There's no playbook for Markoth that you can memorize and train your brain to, while there is for Mantis Lords and Grimm.
Here's a medium-low learnability boss:
How to choose
Which kind of challenge should you design? High learnability lets you balance something to be super hard at first, while letting almost anyone overcome it after a reasonable amount of practice. This makes sense for most video game bosses since they're required to finish the game, have save points right before them, can feel anticlimactic if they don't challenge the player, and are only meant to be fought once. Low learnability lets you balance something so that players don't necessarily need practice to beat it, while staying interesting once they are practiced at it. This makes sense for a reused challenge, or something encountered far away from a save point, or a game designed to be played more than once.