Two characters, one journey
River Tails: Stronger Together is a 3D co-op adventure platformer with a colourful cartoon aesthetic. You play as either Furple, a curious and excitable purple kitten, or Finn, an independent fish with a bit of an attitude problem. The two of them travel upstream toward the icy mountain where Furple's family are in mortal danger, and the whole game is built around an asymmetrical co-op system: the two characters are different, so neither one can carry the level alone. Along the way you cross land and water, exploring rainforests, river caves and a swamp before reaching the icy mountain, and you meet local wildlife that you have to sort into friends and enemies before it's too late.
Playing it together
The game is designed specifically for two players. You solve puzzles and take on a boss at the end of each level, and both of those need communication, coordination and trust between the two of you. The challenges are river-themed and the mechanics and puzzles keep growing as you travel further, so the skills you build early are the ones you rely on in the boss fights. Bosses are protective of their turf and angry about a kitten and a fish getting close, and beating them comes down to staying calm and working together rather than to raw platforming.
Before you start
River Tails: Stronger Together requires a controller in order to play. Split screen and local co-op are supported, and friends on the internet can join through Steam Remote Play Together or Parsec; the developers do not provide support or troubleshooting for those services, so any issues there go to the service's own support teams, and using them means agreeing to their terms. If only one person is around, there is LoneWolf mode, a special control mode that lets you play both characters with a single controller, turning the co-op coordination into a challenge between two halves of your own brain.