Sonic 4 was released in 2 parts, with years between the episodes. It is a return to the 2D gameplay.
The game didn't give a good first impression. First I had to install Java which it needs for the config launcher. Then, when the game does launch, “Enter” took me into the menu, but I had to use “Spacebar” to select items in the menu, and “D” went back. The controls say to use a Red and Green button which is nonsensical. It's like it wanted you to use an Xbox controller, yet Keyboard was the default. The music seemed set insanely loud too.
Like most Sonic games, it starts easy and based on speed, then gets tough with many aspects to slow you down.
I played Sonic Advance recently and one flaw is that the camera is quite zoomed in and Sonic is central which doesn't give you a lot of viewing range. Despite being played on a large TV, this suffers from the same design so you still don't get a good view at what lies ahead. Weirdly you can hold Up and Sonic will have an animation of him looking up, but the screen doesn't pan.
The graphical style doesn't seem to know what it wants to be. It's kind of a retro throwback, but a bit more arty, yet looks a bit low resolution. Sonic looks very shiny, and some animations seem janky (which was also a flaw of Sonic Advance).
The stages are reminiscent of past games but with some new mechanics like the torch puzzles and mine carts within Lost Labyrinth. I think some parts are just directly stolen though. The Lost Labyrinth zone where Sonic slides down a waterfall in an infinite loop until you leap onto the correct platform.
The boss in this zone is so frustrating. You have to do platforming underwater for up to 1.5 minutes. Then when you reach the boss, Robotnik raises pillars in a random pattern and it is one-hit-KO for you. So to try again, you have to do the platforming all over again. All the bosses in the game seem very familiar.
The menu has a level select so you don't even need to play them in order. I'm not sure what advantage the lives system has. If you aren't good at the game, you could run out of lives and then have to restart the level from the start, but with a small stock of 3 lives.
The physics seem a little strange. Firstly, Sonic seems a bit slower and takes longer to reach his peak speed. Secondly, you can stop suddenly rather than gradually slowing down based on your momentum.
If you are a Sonic fan, then you will like this game more than I did. It's not the worst thing to happen to Sonic, but the lack of original ideas makes this game seem very lazy.