idk if anyone else has already figured this out but I did a bunch of math and experiments to figure out how the scoring system works in beatspell in rhythm heaven groove (details and minor "final secret" spoilers under the cut!)
so when you defeat an enemy in beatspell you get points, and at the end of a chapter this is helpfully broken down as the sum of three things: a base score, a time score, and a critical hits score. defeating enemies is the most significant and least self explanatory part of your score in beatspell so it's the only part I'll bother explaining here.
base score
this is a constant value for every enemy type. for most enemies this is 100 points, but it's more points for weird enemies and bosses. in the secret hard mode for random cave quest, this is multiplied by 1.5 to make up for how hard mode is harder.
time score
now if all three components were that simple I wouldn't be making a post about my findings. the time score is exactly what it seems like: you get more points the faster you defeat an enemy, but it's implemented in a nuanced way.
for every encounter, this value starts at 200 points (300 points in secret hard mode), and then after some amount of time which is different for every enemy (I'm pretty sure it's correlated with how much hp they have but also hard coded) it starts ticking down at a rate of one point per beat until it eventually reaches zero. it's theoretically possible to defeat every enemy before this starts counting down at all and thus get the maximum value for this category in every encounter. fun!
critical hits score
this was the part that made me want to do the math in the first place.
as you'll know if you've played random cave quest, there's an item called the balloon which decreases your attack power by 80%, but then increases it back by 5% every time you get a "critical hit". for the balloon, a "critical hit" is defined as a spell cast with perfect timing for all inputs. so getting a critical hit with the flame spell requires two perfectly timed inputs, and getting a critical hit with the lightning spell requires five perfectly timed inputs.
I had initially assumed that this is what the "critical hits" were that this part of the score was referring to, and that you simply got more points the more of these perfectly timed spells you were able to cast.
I tested this hypothesis by spending several minutes in a fight casting cure on myself over and over until I'd gotten dozens more critically timed spells than I would usually have time to get before an enemy is defeated. this resulted in a critical hits score of around 170, which was about the same as my critical hits scores for every other encounter in the chapter. so obviously this score can't just be giving you points for every critically timed spell you cast.
long story short, after carefully examining gameplay footage and taking notes, I figured out that this part of the score is about what portion of your hits are critical hits, not the absolute number. and furthermore, it's actually per input, not per spell.
specifically, it's the fraction of your inputs during the fight that were perfectly timed, multiplied by 200 (300 in secret hard mode), then rounded to the nearest whole number. (yes, it's rounded to the nearest whole number and not just rounded down which would be easier to code. I checked.)
conclusion?
going for high scores in the secret hard mode of random cave quest is so fun that I've just been doing that instead of going for the perfects that I haven't gotten yet in the main game. game of the year
