Physics are slow and stupid with the only way to gain speed being the ability to go from 0 to 100 miles per hour. This sounds good for a Sonic game, but there is rather tight platforming. Also the homing attack is in this game for no reason, the homing attack was introduced to aid 3D Sonic design to help alleviate potentially poor depth perception and precise platforming. This means the level design mostly just boils down to "straight line > ramp > spring > homing attack chain > straight line > level-specific gimmick > ramp"
They reuse designs from older games several times over. There are only 5 worlds in the game each with 4 Acts/levels (including the boss Act) which makes the worlds feel padded out and longer than they need ot be and each of them are just reused. Splash Hill Zone is an obvious reusage of Green Hill Zone in the original Sonic 1. Casino Street Zone is an obvious reusage of Casino Night Zone in the original Sonic 2. Lost Labyrinth zone is an obvious reusage of Labyrinth Zone in the original Sonic 1. Mad Gear Zone is an obvious reusage of Metropolis Zone from Sonic 2. E.G.G. Station Zone is a boss rush of all previous final-act bosses but harder with a 24-hit garbage boss at the end with an insta-kill final attack. Also it's reusage of Death Egg Zone from the original Sonic 2.
The only good song in the game is Mad Gear Zone Act 1's song, and everything else is ear-grating and attempts to be like the original Genesis games, but fails in every format.
Back onto physics, if you let go of movement keys you IMMEDIATELY come to a stop. The Spin Dash, a move typically good for a burst of movement, gives you absolutely 0 momentum. There is no friction in this game and your acceleration is abysmally slow.
Level design is absolutely atrocious, like I said. They will outright kill you instantly for missing a single button input when realistically it was the game's fault because they decided you didn't want to homing attack on the obvious homing attack chain at the last second. There's also a stage that takes place nearly completely in the dark (in a Sonic game, yes). There's also a stage filled with instant-kill crushers while an instant-kill wall is chasing you. The special stages (accessed by jumping into a giant ring by collecting 50 rings by the end of the stage) are like the original Sonic 1 stages though slightly different, as you control the whole stage rather than just Sonic. You bounce around like a tennis ball and there are bumpers to make it even worse, ring gates which force you to collect rings, and a time limit for no reason.
The game also looks atrocious. Everything looks glossy and gleams and shines like it's a freshly polished shoe. Everything just looks like garbage or is reused. Look at the damn Motobug for God's sake. You can literally see how bad it is even in the 1000 enemy kills achievement.
Achievement design is horrible. Defeating 1000 enemies is just grinding the same level over and over again, so is getting 99+ lives, collecting all the rings in Special Stage 1 requires pinpoint accuracy and perfection. Having to do the final stage, WHICH IS A BOSS RUSH WITH HARDER BOSSES THAN THE PREVIOUS ONES, as well as THE FINAL BOSS [b]WITHOUT TAKING DAMAGE[/b] is horrible design because the hit detection and RNG plus the general movement is so poor that it makes attempts unfun. Especially that 4th boss...
All-in-all, this game is a horrible follow-up to the masterpiece that is Sonic 3 & Knuckles. For a true, real successor on the classic Sonic games, please look at Sonic Mania instead. But you already knew that because all these games are old. I bought this game as a joke for the 100% and I hate it. It is not worth it.
