Rain World is a platformer with a focus on stealth, exploration, atmosphere, and AI. Rain batters the surface periodically, crushing and killing everything, so between downpours, you need to leave your den and gather food while evading and dealing with predators. The game will consist of an open world with 12 regions, from the dark underground to the canopy where vultures roam, and different areas and creatures will offer different challenges. The upper regions more on platforming, the sewers with water and swimming and avoiding leeches and using snails, etc. The big thing here is the interaction between species; the game is almost puzzle like in that aspect. If you know how species will react to each other and in certain situations, you can use that to your advantage
So the core gameplay has you exploring the world, gathering food, and finding shelters before the rain comes. While you do have limited moveset, the devs are working on expanding that with more items. For example, snails let out of stunning shockwave when disturbed so you can use them like grenades to gain a few seconds to escape from predators or pacify a swarm of leeches. Another idea was being able to knock the skull covering off a vulture's head and carry it around to ward off lizards.
You're prey in this world. You're supposed to feel outnumbered, outmatched, and pretty much always on the back foot against lizards and vultures and other things. Fleeing and hiding is usually your best option. Your agility is your greatest advantage. When you see a vulture shadow sweep across the screen or a white lizard reveals itself, it's always tense.
But as you master the game and your skillset, you become more proficient. Rather than running away, you could lure a lizard, backflip over it when it charges, and use a stone to knock off a ledge. Or spear a lizard to a wall to distract another hungry predators. The devs have likened the game to a metroidvania; instead of new gear keeping you from areas, it's your own skill. Once you're a better player, you can reach new areas you couldn't before, take on odds and enemies that would have killed you