Honestly don't know why they removed the ability to add HP with +, current HP and Healing system isn't exactly fun or interesting.Wow, enemy density is WAY up and he removed the ability to add HP with + (you can still lose HP with - though :^)). Even without cheating in HP the Bio Research Lab used to be a breeze, now I'm having a hard time getting through it due to there being a shitload of enemies in every room and your stamina regen continuously gets worse the lower your HP is. It's a snowballing effect where you lose HP, can't dash/hit as often and then lose more HP as a result. There are seven (7) catboys and a wasp in the first real (ie, not the lobby) room of the Lab and they're not spread out either, it's just 5 on the bottom floor and 2 on a slightly higher level ready to come down. It's not that they're hard to kill, but you're pretty much guaranteed to get hit. On top of that, enemies respawn when you leave a room and backtracking is required to finish the level so you're just gonna have to fight them multiple times and when there's 7 catboys flying through the air ready to fuck your ass, one is bound to land it.
I'm no stranger to difficult games but I can't say it's something that gets my dick hard. If it sounds like I'm just angrily complaining, sorry, I'm just trying to voice my opinion on meaningful gameplay changes as I see them, not be an asshole.
I don't have much issue with the current balance of the game (though Sam is now significantly harder to play as versus Whispy, namely because of their fast attack also pushing them forward, and their heavy attack being way too expensive to be useful, while also accomplishing very little compared to Whispy's heavy) as it seems to be to make weapons more useful, which I think is fair considering before I've never bothered with weapons, while I did end up using the shotgun on the boss to finish off the level, buying 12 ammo to chunk 75% of the boss' health.
My strat for easy clearing was to just use dash + jump + X attack to finagle enemies into stacking then do 3-4 hit combos, dashing out or end with a heavy attack as Whispy. Keep distance for a bit to regen energy, repeat. Same strategy works as Sam but significantly worse. Also you can always just run past enemies in every room except for the one room where you're locked in.