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