In a nutshell, it's an excellent narrative game with highly developed characters, meaningful choices and an incredible soundtrack.
Despite the score it gets here, it's actually a very good game. The story takes places in the future. Sea level rose so much that there no land anymore. Humanity lives on small artificial islands. The plastic pollution is everywhere. Despite this very dark premise, the world is colourful.
At its core, it's a narrative game. Each level lets you take lots of decisions: will you help the people or mess with them? Will you try to save humanity? Will you share resources or take everything for yourself? The most innovative feature is that before each level, you have to choose one other player to follow. You'll face the level as (s)he left it. If (s)he let resources for you, you'll be able to take it for free. If (s)he helped the people, they will welcome you, but if (s)he messed with them, you'll have to face the consequences of his/her actions. If you buy resources from shops, they won't be there for the next player, unless you pay an extra to let the shop keeper refill his stock.
Fortunately, before choosing who to follow, the games informs you about his/her play style. So you can choose the one that best fits your need. For example, every time you let resources for the next player, you fill your "cooperative" level. This level is shown on player selection screen. So pick the player with the highest cooperative level to increase the chances to follow someone who let resources for you.
Another thing I loved about the game is its resource management borrowed from survival games. You begin the story with a plastic pollution infection. At the end of each level, you lose TWO health bars. The only way to increase your health is consuming the most rare resource of the game: ozen. Everyone wants ozen because everyone is sick. Will you give this bottle of ozen you have to this near-death NPC? If you don't, he might die soon. But if you do, you can be the one dying soon ... In addition, the more the story progresses, the rarer ozen is. Careful resource management through the entire game is essential because near the end, you'll be desperate for ozen (remember that you lose two health bars after every level).
I'll give you some spoiler-free hints I would have liked to know before playing:
1. Stay almost always at 1 health bar. The only time you need more health is just before finishing a level. At that time, consume two bottles of ozen to be at 3. You will be back at 1 a few seconds later.
2. Always keep at least 4 bottles of ozen.
3. Select the player you follow carefully. Take a player whose goals are aligned with yours: it improves the chances (s)he made choices that match your own.
On the "online dependent" side. It's really completely DRM-Free. No activation or login is required. Online features are only used to publish on the server the state of the level as you left it, and to fetch the state of the level you enter as the player you follow has left it. You can play completely offline. The only consequence is your player-to-follow options will be limited to hard-coded ones.
By the way: works perfectly on Linux. I played it using the Heroic Launcher. No issue at all.
Have fun