Sonic 2 is one of those games where I really really hate it at points, but at other times it is amazing, honestly this game leaves me with a lot of mixed emotions.
This game or well the original version of it, introduces Spin dashing (which was possible in the sonic 1 port for mobile devices as well), Super Sonic, Tails, and two acts per zone instead of three (meaning more unique zones in total). These are all pretty good features and have become a staple in the series since and why I like the franchise.
Sonic 2 honestly has pretty good level design, half of the time, and well the other half of the time it falls flat right on it's face. I am glad the level design for the most part has improved since Sonic 1 because I don't think I could handle more of that. Unfortunately 2 of the worst zones Chemical Plant starting with ACT 2 and both Aquatic Ruins acts are as bad as the worst levels from sonic 1 for me and it especially sucks they're the 2nd and 3rd zone respectively. Chemical Plant Act 2 just has downright unfair level design that punishes you for making a simple mistake and it's especially true for Aquatic Ruins (the worst of the two for me) where sometimes you get hit by random dropping pillars or an arrow that shoots from the left of the screen at random and is hard to see which is a problem the stage has in general because it's colours are wayyyyy too bright. Luckily unlike sonic 1, there are zones I enjoy more than just the first one (in this case Emerald Hill Zone) with Casino, Hill Top, Mystic Cave, and Oil Ocean) all being highlights for me as well as the first stage.
However, the rest of the stages are pretty mediocre and feature not great level design like what was seen in the first game. Metropolis zone ACT 1 and ACT 2 are mediocre with some minor unfair level designs that could kill you randomly, but for some reason this stage has 3 ACTs and the third one is EXTREMELY hard and unfair and I'm not really sure how I got past it. Lots of cheap deaths in this level in particular. Sky Chase zone is unique and that you're on a plane flying throughout the whole level, but there's no ground and Tails will go under you when you fly and it just doesn't feel quite right and like I'm about to fall at any moment along with some minor enemy spam. Wing Fortress is solid, but there's one part where you can't see very well to the right of you and you're expected to make basically blind jumps and hope you get to the other side which basically ended most of my runs on this level and was frustrating.
Then there's Death Egg zone which is the stage I'm the most mixed on, this game is downright unfair on the original version of this game and I would have rated this game like 2 stars otherwise, but it gets an extra half star due to saving. Without saving you're expected to fight 2 boss fights in a row (20 hits total) with zero rings and the bosses have a set pattern as well that you're expected to memorise. I HATE these bosses, but I found myself having more and more fun trying to speedrun this stage the more I tried it and I ended up loving it. However what isn't fun is the hitbox on Eggman, the game doesn't properly display how to beat this boss and it is frustrating as hell without looking it up and even with looking up how to beat the boss it took me 2 hours, and I... kind of liked it? It felt fun towards the end and felt extremely satisfying to defeat the bosses and see the credits roll. Honestly, if I didn't have fun on this stage by the end, I would have rated this game 2 stars even with the saving feature.
Besides the levels, the rest of the bosses are pretty okay to fun. There is one weird oddity with the mobile version in particular, which is the fact there's a Hidden Palace Zone (which was scrapped from the original release of Sonic 2), it's an okay stage (not anything too special), however if you die on the stage it sends you back to Mystic Cave (which is how you enter it) which is annoying for trying to find the level again. I ended up not defeating the boss due to this.
Overall, I love and hate this game and it's left me feeling very mixed about it. The level design is all over the place from very high highs to very low lows without too much in-between.
This game or well the original version of it, introduces Spin dashing (which was possible in the sonic 1 port for mobile devices as well), Super Sonic, Tails, and two acts per zone instead of three (meaning more unique zones in total). These are all pretty good features and have become a staple in the series since and why I like the franchise.
Sonic 2 honestly has pretty good level design, half of the time, and well the other half of the time it falls flat right on it's face. I am glad the level design for the most part has improved since Sonic 1 because I don't think I could handle more of that. Unfortunately 2 of the worst zones Chemical Plant starting with ACT 2 and both Aquatic Ruins acts are as bad as the worst levels from sonic 1 for me and it especially sucks they're the 2nd and 3rd zone respectively. Chemical Plant Act 2 just has downright unfair level design that punishes you for making a simple mistake and it's especially true for Aquatic Ruins (the worst of the two for me) where sometimes you get hit by random dropping pillars or an arrow that shoots from the left of the screen at random and is hard to see which is a problem the stage has in general because it's colours are wayyyyy too bright. Luckily unlike sonic 1, there are zones I enjoy more than just the first one (in this case Emerald Hill Zone) with Casino, Hill Top, Mystic Cave, and Oil Ocean) all being highlights for me as well as the first stage.
However, the rest of the stages are pretty mediocre and feature not great level design like what was seen in the first game. Metropolis zone ACT 1 and ACT 2 are mediocre with some minor unfair level designs that could kill you randomly, but for some reason this stage has 3 ACTs and the third one is EXTREMELY hard and unfair and I'm not really sure how I got past it. Lots of cheap deaths in this level in particular. Sky Chase zone is unique and that you're on a plane flying throughout the whole level, but there's no ground and Tails will go under you when you fly and it just doesn't feel quite right and like I'm about to fall at any moment along with some minor enemy spam. Wing Fortress is solid, but there's one part where you can't see very well to the right of you and you're expected to make basically blind jumps and hope you get to the other side which basically ended most of my runs on this level and was frustrating.
Then there's Death Egg zone which is the stage I'm the most mixed on, this game is downright unfair on the original version of this game and I would have rated this game like 2 stars otherwise, but it gets an extra half star due to saving. Without saving you're expected to fight 2 boss fights in a row (20 hits total) with zero rings and the bosses have a set pattern as well that you're expected to memorise. I HATE these bosses, but I found myself having more and more fun trying to speedrun this stage the more I tried it and I ended up loving it. However what isn't fun is the hitbox on Eggman, the game doesn't properly display how to beat this boss and it is frustrating as hell without looking it up and even with looking up how to beat the boss it took me 2 hours, and I... kind of liked it? It felt fun towards the end and felt extremely satisfying to defeat the bosses and see the credits roll. Honestly, if I didn't have fun on this stage by the end, I would have rated this game 2 stars even with the saving feature.
Besides the levels, the rest of the bosses are pretty okay to fun. There is one weird oddity with the mobile version in particular, which is the fact there's a Hidden Palace Zone (which was scrapped from the original release of Sonic 2), it's an okay stage (not anything too special), however if you die on the stage it sends you back to Mystic Cave (which is how you enter it) which is annoying for trying to find the level again. I ended up not defeating the boss due to this.
Overall, I love and hate this game and it's left me feeling very mixed about it. The level design is all over the place from very high highs to very low lows without too much in-between.