Let me preface this by being as blunt as I can possibly be:

Rain World is BRUTAL AND UNFORGIVING. Period. I know it, you know it, and your (slug?)cat knows it.

But here's the thing:

The developers know it too. They knew it from the start of pre-production to the final Beta test, and they're damn proud of it.

When Joar Jakobsson and his team first conceived the idea of Rain World, the main goal was emulating what it meant to be
a "rat in Manhattan." And let me tell you, these people succeeded.

The entire design ethos of Rain World centers on one core focus: Knowledge. Or rather, the notable lack of it the player has.
Every aspect of Rain World is focused on the player surviving and understanding in equal measure. As Sun Tzu once said: "If you know the enemy and know yourself, you need not fear the result of a hundred battles." This idea holds as true in Rain World's dilapidated, alien slums as it did in ancient feudal China. Whether you're watching a new, strangely-colored lizard on the hunt or throwing rocks at a suspiciously pulsating metal pole, uncovering knowledge about your enemies is a the crux of Rain World's gameplay. This, of course, works smoothly in tandem with it's Metroidvania roots. The plot of the game revolves around exploration, as the main quest involves your protagonist being separated from their tribe. The gameplay reinforces this, as the sparse, arbitrary placement of shelters and constant time pressure mean the player is constantly either looking for new shelter or shortcuts to previous havens. Even backtracking is useful in itself, as one will find themselves both looking for new sources of food or revisiting already established ones.

However, Rain World's Metroidvania roots are not without their own twists. The game at the same time painfully deliberate and frenetically fast paced. Your player character is a "slugcat," and is about as strong and durable as that name implies. You are almost at rock bottom in this world's food chain, and the game takes great pleasure in reminding you of this. Almost every creature or entity you encounter in the game's warped ecosystem wants to kill you, eat you, or both. The slightest misstep or smallest provocation could land you in the tentacled jaws of a Vulture, or the dark tunnels of an eager Lizard. Quick, informed decision making is of the utmost importance here, and is the key to survival in this ruthless world order.

Of course, I also have to talk about the game's GORGEOUS pixel art and animation. I didn't think one could actually mix pixels and physics-based ragdolls, but Rain World does what it does best and blows away my expectations. The procedural animation is so fluid you'd think it was motion-capture. All the predators and prey move and act in highly believable ways, and even when they don't the occasional glitch or bug merely adds few laughs in an otherwise tense situation.

Rain World feels like a game I always wanted but could never quite conceive. Like the proverbial Extra-Chunky Spaghetti Sauce, it's existence created a desire for something I wasn't even aware of. Whether you go in blind, check the wiki (Highly recommend you do this: https://rainworld.gamepedia.com/Controls), or watch a walkthrough, Rain World is an intense, unnerving, captivating ride akin to a video game version of Attenborough's Planet Earth. I highly recommend.

I recommend this game to everyone, who likes 2D platformer games
and very challenging difficulty. In my opinion this game has the best AI of all 2D games i have played and very nice looking art style.
I absolutely love this game :D .

Yes, this game is hard. Yes, this game is diffficult. Yes, this game is unfair. But this game is so much more (and if every game were effortless, we'd be dreadfully bored). I'm serious. It is a lot more mysterious and complex than you might think.
I recommend it to people who have a good grip on their rage levels, and who understand the challenge. As they say, difficult roads often lead to beautiful destinations.
I love it, and can't tell you how many memories this game has given me. If you already have the game, don't worry. It gets easier as you adapt and bond to your slugcat. It may not get easy, but it will get easier.