KarmaZoo from Pastagames says that online co-op with strangers needn't be the painful exercise it usually is. A co-op platformer you play online with random players (or friends if you like), groups of up to 10 must work together to get through a short series of levels, and it works a treat.
The design is pretty ingenious. After grouping up, players have to get through four stages, chosen from a pool of 300 based on which characters are in the party. You'll expire if you're alone for too long, so you have to stick together. Dying to spikes or other hazards leaves behind a tombstone, which allows everyone to cross safely while it lasts. Best of all, each level has simple co-op puzzles, like opening doors to let others pass through, or forming a line to get electricity from one lightbulb to another. And everything you do that helps other players earns Karma, a currency you all accumulate together, which can be used to unlock new characters and more.
Each character has its own ability that further helps the cause. All of them can double jump and sing, but some can cross spikes unharmed, some can glide, some can destroy special walls, and so on. There are over 50 characters, and while some abilities are definitely better than others, you're encouraged to play as them all in order to complete each one's missions.
The game and level design means players really do work together, and it can be great fun in short bursts. There's real joy to be found in the main Loop mode and in Totem — a competitive party mode. However, it can all become quite repetitive. Even as you discover new levels, they all boil down to the same few ideas, including some mechanics you'd rather not see multiple times, and the characters all play roughly the same despite their unique skills.
All that said, KarmaZoo gets a lot more right than it doesn't. Ultimately, it succeeds in delivering a simple but fun experience, and its clever design means players behave positively and altruistically. If you're looking for an online game with good vibes and friendly co-op, this is it.