This time around there are twelve playable characters, but you always play as a whole team of three at once and these teams are: Team Sonic (Sonic, Tails and Knuckles), Team Dark (Shadow, Rouge and Omega, a new character), Team Chaotix (Espio, Vector and Charmy, some returning classics) and Team Rose (Amy, Big and Cream, who is making her first 3D appearance). Right away, we have a problem with the game. You essentially control one of the three at a time (the other two just follow) and every team has a 'speed', 'power' and 'flying' character and you regularly need to switch between them in order to get through any level. In a hurry, the switching around is awkward and can often unfairly lose you a life. It just feels like a like a bad idea they added to try and make it unique.
Also, each different team has their own storyline and all the stories tie together, but other than a few cutscenes, there's very little focus on story this time, which is a shame with the last two console Sonic games having excellent stories. What's also annoying is that with the four teams, you're essentially going to be just playing through all the same levels (albeit with slight differences) four times. A lot of the levels aren't that great either, with many sections where you'll run off a ramp or something and then miss the platform you're supposed to land on for seemingly no reason. The whole game is full of sections that don't work properly, which can make things very frustrating, when you keep dying because of things that are out of your control. I also struggle to understand why any of these levels exist within the fictional universe, they all just seem to be for the gameplay and have no real justification.
Remember how I said that you have to do the same levels four times? Well, that will only be the case if you're really lucky. To actually get to the game's ending, you have to collect all of the Chaos Emeralds, and to get all of the Chaos Emeralds you have to find these keys hidden in levels, then not get hurt at all until you win. This alone is pretty hard, but then after this you have to win an extremely difficult 'special' stage, The 'special' stages have you running through these weird tubes in order to catch a Chaos Emerald (which, for some reason, is flying away from you) and you have to go as fast as you can (collecting speed orbs and avoiding spike bombs) to get it. It sounds easy, but it's really hard because it's so horribly glitchy that you're going to need to try so many times and, to be clear, you have to win a level with a key every single time you want another try at the 'special' stage...
So, that's about it. It's not all bad (parts of it are good) but it is still quite bad. Probably worth trying if you know you like Sonic, but not if you aren't very familiar with the series and certainly not as your first exposure to it. Also, I played the Gamecube version of the game and, sadly, the other versions are even worse (in terms of glitches). Rating: 6/10