i really like the concept, and it's pretty fun to play;
though it could really use a proper save system because, while the grinding is not that tedious, the game is prone to freezing whenever something happens at the same time as you interact with a passenger (either picking them up, or dropping them off).
usually involves crashing into something (i had one happen as i was picking up a passenger and crashing into a vehicle, and another when crashing into the road after flying with boost into it, while dropping a passenger at the same time thanks to NoSlow)

the various upgrades are fun but i think some of them could be streamlined.
there's no reason to have vacuum, evil and noslow tied to a button.
having a lot of buttons to juggle with can be cumbersome; sometimes less is more.
i also have some doubts about every single upgrade giving you a visual overhaul: normally that's a good thing but with so many of them at once it just gets silly. would be nice if there was at least an option to turn them off (visually only. keep the upgrades).

there's no reason why you wouldn't want evil to be on at all times (since it only works on living things specifically; you still lose money yourself if you actually crash into something).
noslow is also a really good contender to be always on, since dropping off passengers immediately saves you a lot of money that would be lost wasting time trying to stop (i can see it being annoying if always on for the picking-up part of the minigame, but if it worked permanently only for drop-off that would be good).

when you have max boost (and maybe max glide?) enabled, if you touch the ground while coming down from flying, you'll "bounce off the road", and be immediately turned around from the direction you were facing before.
gets fairly annoying because max boost is already hard to control, so this makes it even more difficult to work with since half the time you can't land properly when it's enabled.

nothing much else to add tbh. the game's solid.
i had a minor gripe with how passengers' fares are calculated seemingly based on "direct distance from goal" (sometimes you have to do a massive roundabout trip to stay on road while the fare is real low due to being close to the starting point) but i assume that's because you can always fly directly to any target once you get the right upgrades.

good game

EDIT: found the ending that gives you permanent evil mode (allegedly) so that's fun. unfortunately as soon as you get the ending you're thrown spinning off the map and reset doesn't work.
so it works as a finite ending, but you don't get to keep the unlock because it's a softlock and there's no save data system

the upgrade system and base stats need a bit of a revision due to how the different characters work.
luna works fine; you can easily tell the game was made with her kit in mind, since after you get far enough into the game you really feel overpowered and that's what good games are all about.

because of this, xelvy's gameplay feels a bit odd to play around.
(there's an inconsistency between her in-game name and the description name, so i'll just use the in-game one)

for starters, all upgrades related to spell damage and bullets only affect the supporting magic, meaning they don't feel nearly as impactful as they do when playing luna, because they don't improve your "main" way of attacking.
for that same reason, the "additional bullet" upgrade is completely useless as it has no effect (it doesn't increase the amount of bombs you drop at once, nor the total amount of bombs you can drop) since it doesn't affect the supporting summoned magic either; it should probably be removed from xelvy's upgrades rotation entirely.

i'm not sure if there's a cap to the amount of "additional bullets" upgrades you can roll, but i never managed to get more than 2 (total of 3 bullets) when playing with luna. which is fine and all if it's intended.
however, in xelvy's case, you can keep rolling "additional bomb" upgrades indefinitely, even though you can only drop at most 8 at any given time (regardless of upgrades, that's the max frequency xelvy can drop bombs at before the start exploding).
there should probably be a cap of 7 upgrades and once you've gotten all of them they stop appearing in the rotation.
there's also a similar situation with crit chance. you can hit 100% crit chance, and crit chance upgrades will still show up. probably should make it so they don't once you're maxed out.

the stats table needs a custom revision for each character. in xelvy's case for example you get the same stats as luna but not all of them are applicable (like the bullet bonus amount, which as mentioned does nothing).
her main gimmick is entirely missing for example (notably the number of bombs, or their "blast speed", which is mentioned in one of the upgrades).
her bombs base damage seems to be accounted into base fire damage.

also, and this is mostly unrelated. i feel like there's really no incentive in taking any max hp upgrade.
while you do want to mostly focus on damage output, everything else has at least some use that makes you consider taking at least one of them.
however having more max hp doesn't feel "important" at all, since you'd rather take hp regen in case you get hit, or even speed so you can try not getting hit in the first place.
i'm not sure after which amount luck stops making a difference, but even banking on extra (maybe useless) luck feels more rewarding than taking max hp. though i'm not sure how you could make that any better.
maybe merging the two hp upgrades and lowering their effectiveness? (something like, +5hp, +.3 hp regen, as a single upgrade)

i've encountered a bug where i died on the second boss for apparently no reason.
i did a stinger, canceled into up + mid-air kick near the right side of the screen, and immediately got a game over screen even though i was mid attack, nowhere close to low health and had an extra life.

also those crocodile enemies are extremely annoying.
if you attack anywhere close to them they jump away, and if they jump forward they have an hitbox. i also have no idea what's the counterplay for when they get enraged and start rolling into you, besides getting hit.
the only way i've been able to hit them at all is using stinger because it's the only attack that covers horizontal distance, with varying degrees of success.

EDIT: the robbers are also pretty annoying but that's because i haven't figured out a chain to dispatch them before they start shooting me to death.
is it possible to increase the movement speed or the time to chain your combo a bit? i can barely walk from one area to the next before the first new enemy to keep the combo going shows up. it's really difficult to do anything with the combo system as it is