Some other thoughts.
1. The balancing isn't quite right in the beginning. What I mean is it feels like most characters aren't ready to take on the second level until they're fully upgraded (except for the bonus 1% upgrades). It really would be more fun to feel like it's not a pointless waste of time trying to go onto another level beyond the first one before a character is fully upgraded.
There's no real reward for trying to take on a level beyond the first one until a character is fully upgraded either. Because with the deck stacked against you so hard past the first level until you're just about fully upgraded, and dying resulting in any time spent on the level practically going to waste (because you earned maybe a handful of soulstones if you didn't succeed), trying to play the second level until then is more an exercise in frustration than anything else.
But it gets boring having to play the first level multiple times with most characters before that character can reasonably move on from the first level. I've played the first level much more often than any other level specifically because of this - because I felt forced to by the level scaling rather than because I wanted to - and that's getting more monotonous with every new character unlocked because then you have to go do that again every time. Unlocking characters isn't exciting anymore. It just means I have to grind the first level yet again.
2. The damage from those obstacle trees in the marsh is excessive. I saw today that running into a tree a single time - just one hit - took an entire half of my health away. Why? Why have them cause so much damage? I did only have armor upgraded once at the time, but still. Half your health in a single hit? Why? Bosses don't even do that much damage. And this is only the second level.
There are also so many trees around sometimes that it's kind of ridiculous. I have had times where I have been lost with tons of damaging trees all around me and it's taken several minutes to find my way out of them to somewhere there was at least some reasonable area available to dodge.
The amount of damage caused, and the amount of damaging trees in some places, really does not seem in like with difficulty for a second level.