If I were to tell you âRain World has the
most complex ecosystem of any game,â you might go⌠âWhat?â Because Rain World doesnât seem particularly
advanced â itâs a 2D pixel art game where you play as a weird slug, how complicated
could its world really be? While there are other games with fancier graphics
and denser lore, Rain Worldâs unique system of procedurally generated animation and complex
AI come together to simulate the feeling of a living ecosystem better than (almost) any
other game Iâve played. So, for this entry into the archive, weâll
uncover the fascinating intricacies of Rain Worldâs pixeled biosphere. Now, letâs become part of this virtual food
chain⌠Rain World begins with a cutscene showing
a family of weasel-like creatures called Slugcats struggling to survive. A storm breaks out and a young Slugcat, the
protagonist, falls into the drains below, and awakens in a new and unknown environment. The game then quite literally drops you into
the ecosystem. Itâs disorienting at first, but pretty quickly
you learn how to live like a Slugcat. In this world, you are small but crafty, able
to catch and feed on small creatures like the fluttering Batflies. But from your first steps, the animation feels⌠different. And thatâs because it is. Like most of the creatures youâll meet in
Rainworld, the Slugcat is procedurally animated, meaning its animation is determined in real
time through code interacting with the gameâs environment. Since the dawn of animation, pretty much the
only way to get a creature to move has been to hand animate it moving frame by frame. But in Rain World, a creatureâs motion happens
organically within a set of predetermined parameters, creating movement that feels uncannily
spontaneous. One mind-blowing example of Rain Worldâs
complexity are the Lizards. These enemies move with procedural animation
just like the Slugcat, able to run across flat ground, crawl through tunnels, and climb
up poles. But they take this to another level with their
AI. When one lizard catches you, it will try to
drag you back to its den. But if another lizard passes by, its AI will
cause it to try and snatch you for itself, which can give you a dynamic opportunity to
escape. But thatâs just scratching the surface of
lizard complexity. Each lizard also has their own simulated personality
based on six unique modifies that determine how they interact with each other. And on top of that, there are nine different
types of lizards in this game, all with their own distinctive abilities and behaviors. For example, Yellow Lizards have long antennae
that allow them to communicate with each other, meaning their AIâs work together to surround
the Slugcat or cut them off using the terrain. White Lizards can camouflage with whatever
pixels are behind them in their environment, so they hunt by staying completely still until
the Slugcat gets close, then lash out and try to pull the Slugcat in with their long
tongues. Cyan Lizards can use bursts of energy to pull
off incredible jumps that when paired with their AI leads to some of the most hilariously
unpredictable movement patterns Iâve ever seen in a video game. And thereâs another hidden system that can
go completely unnoticed by the majority of players â if you consistently feed a lizard
their preferred food, they will eventually become your ally and start following you around,
and will even get into fights with other lizards that try to eat you. Itâs a surprisingly detailed system that
shows just how meticulous Rain World is when it comes to its ecosystem. In the next region of the game, far larger
predators called Vultures sometimes swoop in from above on nightmarish wings. Vultures will also climb after the player
and squeeze through gaps â their procedural animation particularly uncanny. While vultures are intimidating, as scavengers,
they can be scared off if you stand your ground and throw spears at them, which will sometimes
cause them to drop their masks â seemingly implying these predators arenât entirely
organic. If you hold a vultureâs mask in front of
you, most creatures will run from the playerâs Slugcat, instinctually scared off by your
resemblance to a top predator. Giant orange Centipedes also lurk in the recesses
of this ruined landscape. If one catches you, theyâll admit a lethal
electric shock. Like clockwork, the centipedes move with a
general sense of coordination. Indeed, much of Rain Worldâs ecosystem follows
a similar pattern, with the titular rain that comes every so often marking the end of each
cycle. When the rain falls, all lifeforms must hibernate
or drown in the downpour. Soon, the player settles into these cycles,
and feels like a small part of the larger biosphere. Following the dripping pipes deeper underground,
the Slugcat plummets into a kingdom of waterlogged tunnels known as the Drainage System. Swarms of Leeches writhe in these half-flooded
chambers. When the Slugcat is close, the Leechesâ
AI causes them to go into a frenzy, following the Slugcatâs movements and waiting for
the chance to latch on. If the Slugcat slips, their best chance of
survival is getting back above the water and shaking them off. For unlike the Leeches of today, these blood-suckers
arenât just parasitic â theyâre predatory. Leech swarms coordinate to drag prey down
to the depths, drowning whatever unfortunate creature they can latch onto. Yet one species uses this to their advantage. Squidcadas are cuttlefish-like creatures that
flutter along on four small wings. To feed, Squidcadas have learned to âfishâ
for Leeches by diving into the water and letting one latch on. The Squidcada then flies off with the careless
parasite, feeding on them a safe distance away. Itâs a remarkably dynamic behavior, and
one you can go the whole game without seeing if you move too quickly. The Drainage System eventually washes into
the Garbage Wastes: an entire ecosystem of decaying junk. Yet there is life here in the form of the
inquisitive Garbage Worms. These long, stretchy creatures are something
of a nuisance, with their curious nature causing them to steal spears from the Slugcat when
given the opportunity â often snatching them directly from the Slugcatâs hand. When no spears are in reach, Garbage Worms
will stick their heads in the grime and start sucking up matter, suggesting that they feed
on inorganic material. While normally passive, make a Garbage Worm
angry and they will go on the attack â flinging the Slugcat around with their heads or even
holding the unlucky creature underwater in an attempt to drown them. Groups of Garbage Worms will even coordinate
their attacks, their eyes turning red to indicate their hostility. In the murkiest depths of the Garbage Wastes,
a true nightmare stirs. Hauling themselves up from the depths, the
menacing Brother Long Legs probes for their next meal. Though made of a large, bulbous mass with
several ravenous tentacles extending from their core, the Brother Long Legs are flexible
enough to squeeze through tunnels. Unable to hear or see, they rely entirely
on touch to find prey. And when a Brother Long Legs latches on, they
refuse to let go â eventually wearing the creature out and drawing them in to an unseen
mouth. Where these monsters came from is a mystery
that can only be solved by venturing deeper into this hostile environment⌠The Garbage Wastes empty into the floodwaters
of the Shoreline. Here, a drowned empire of crumbling monoliths
greets the Slugcat. Itâs impressive the sense of melancholy
the pixels on screen can produce. Blue Leeches swim in these waters, a coastal
variant that is larger and more aggressive than their red counterparts, able to pull
the Slugcat under in seconds. If you manage to avoid the leeches, thereâs
plenty of other dangers here. Even the plants of the Shoreline are carnivorous
â with the terrifying Monster Kelp ready to swallow you whole if you get too close. Sensitive to movement, Monster Kelp is difficult
to sneak past. In pursuing the Slugcat, these plants will
twist and contort in unexpected ways, and feel particularly âaliveâ due to their
adaptable behavior. Behind the scenes of the Monster Kelpâs
AI, each strand of kelp moves in accordance with the Slugcatâs position instead of following
a predetermined path. When paired with the gameâs physics system,
the Monster Kelp feel truly unpredictable. And killer plants arenât the only threat
below the waves. Packs of giant Salamanders pursue the Slugcat
with lethal determination. Able to hunt on the land as well, these amphibious
predators share the long tongues of lizards â and seem to be a related species. The only defense the Slugcat has is to swim
with all their might. For a quick boost of speed, the Slugcat can
catch a ride by grabbing onto a Jetfish. These fast-moving aquatic lifeforms expel
jets of liquid to create large amounts of momentum, which can be used to rocket out
of the water. On land, Jetfish arenât always the most
graceful, but in the depths, they make exploring much easier. Yet dive too deep and youâll find monsters. Leviathans are among Rain Worldâs largest
and deadliest predators, able to outpace and swallow a Slugcat in just a few seconds with
their powerful clamping jaws. Seemingly a mixture of metal and organic parts,
Leviathan are the first definitive proof that not all the life in Rain World is naturally
occurring⌠The beings who made the now-ruined structures
of Rain World â a mysterious group called the Ancients â seem to have disappeared
long ago. Yet there is another intelligent species that
has learned to pick through their remains â the Scavengers. These early tool crafters might have the most
impressive AI across all of Rain World. Scavenger behavior is insanely complex, not
just in terms of how they interact with each other, but in terms of how they interact with
you. Though itâs easy to miss, scavengers attempt
to communicate with your playerâs Slugcat through a litany of distinct gestures. If they think the Slugcat is a threat, theyâll
point their spears at them. If you move closer, theyâll try to send
a warning by raising their spears up. If you persist, they wonât hesitate to stick
you full of spears. But if you play it cool, theyâll do the
same. All Scavenger behaviors work on a ârepuationâ
system, where they remember the playerâs actions and respond accordingly. For example: sometimes youâll come across
places called âtolls,â where Scavengers wonât let you pass unless you trade them
something interesting. And they even have a custom animation to let
you know that you havenât paid yet. But if you do trade you something valuable
like a pearl, theyâll sort of wave you through, letting you know âyouâre good.â Trading gets more complicated with Merchants:
specific Scavengers that can offer you unique technology. When a Scavenger wants a specific item, theyâll
kind of paw at the ground or reach out to the item to let the Slugcat know theyâd
like it. And if you give them the item, theyâll drop
something in return, like a lantern you can use to light your way through the dark. Or these blue orbs called flashbangs that
release a disorienting burst to blind enemies. But if you take something from a merchant
without offering anything from return, theyâll go on the offensive. And Scavengers wonât just mindlessly chase
after the Slugcat and then give up. If your reputation gets low enough, they will
actively seek the player out, even sending hit-squads to the Slugcats general location. It all comes together to create encounters
that at their best feel like youâre interacting with something truly intelligent. With a Scavenger lantern in hand, the Slugcat
can explore the dark, decrepit wreckage of the Shaded Citadel â another ruin the Ancients
left behind. Within the forgotten lower pathways, thereâs
no telling what awaits. The monstrous Wolf Spiders scurry through
the dark. Like most species in the Shaded Citadel, these
spiders react dynamically to light sources, and will generally avoid your lantern. But given time, hunger overcomes their fear. And where there is one Wolf Spider, there
are invariably others. Best to keep your lantern close. But not all creatures in the Citadel are quite
so horrifying. Lantern Mice are passive, bio-luminescent
rodents that hang from the ceiling with their long tails. In these shadowy caverns, they are a welcome
source of light. Lantern Mice are notably skittish, and will
run in a panic from the Slugcat if they get too close. And Lantern Mice have good reason to be nervous. Skittering on countless legs are the aggressive
Coalescipedes. When they go on the attack, these disturbing
predators resemble giant centipedes. Yet in actuality, they are made up of numerous
spiders that procedurally combine into a chain when on the attack. Because each spider is an independent AI enemy,
getting swarmed feels all the more overwhelming. The best way to defeat the Coalescipedes is
with the bright light of a flashbang, which stops the scuttling terrors in their tracks. Eventually, the Shaded Citidatel gives way
to the bleak Memory Crypts. Patrolling this region like nightmarish sentries
are the shadowy Miros Birds. Though difficult to spot in the darkness,
these creatures seem to be biomechanical â with metallic legs and scissor-like beaks. Flashbangs are the only effective deterrent,
with the bright light causing their eyes to flash different colors, allowing the Slugcat
to sneak past. Eventually, you arrive at the underside of
a massive structure engulfed in a green electrical storm. Entering the structure, the Slugcat finds
many rooms lack gravity due to localized disruptors. These zero gravity rooms can be challenging
to move through, but the more you see, the more the entire superstructure comes to resemble
a giant computer. And at the heart of the supercomputer, a god-like
artificial intelligence is waiting. This synthetic lifeform is another creation
of the Ancients, and possess the peculiar name of Five Pebbles. Using their incredible power, Five Pebbles
alters the Slugcatâs brain, allowing them to understand the Ancientâs language. Five Pebbles dispassionately tells the Slugcat
that a form of âascensionâ is waiting for them if they keep heading west, before
turning the gravity back off and sending you away. Five Pebbles isnât the only of these AIs,
called Iterators, that the Ancients created. In a forgotten corner of the Shoreline, the
unusually named âLooks to the Moonâ wastes away. If you speak to her, sheâll explain that
AI cannot ascend in the way the Ancients or the Slugcat can â a limitation that has
driven the Iterators that still function to despair⌠As the Slugcat leaves the Five Pebbles supercomputer,
they need to sneak past the gargantuan Daddy Long Legs. These oversized relatives of the Brother Long
legs can hear the Slugcats footsteps, emitting blue rings of particles when a noise is detected. There are hidden lore details that suggest
Five Pebbles is actually the one who created the Long Legs â one of many horribly failed
attempts to fix a decaying world. Behind the scenes of the Long Legâs AI,
each tentacle procedurally searches for surfaces to latch onto â creating an unsettling yet
strikingly natural pattern of movement. Continuing along the underside, the Slugcat
bumps into the bizarre grappling worms. These small, tubular creatures suspend themselves
from the walls on sticky pink appendages â a trait the Slugcat can take advantage of. By grabbing onto a Worm, the Slugcat can use
them like a living grappling hook to swing to new areas. To make their way to the place of ascension,
the Slugcat must climb a massive exterior surface known simply as The Wall. And this region has perils of its own. Pole Plants are cleverly hidden predators
which, at a glance, look like any other pole to be climbed on. Get too close, and the plantlike carnivore
will spring to life, flaring out its red leaves and dragging the Slugcat into its den to be
devoured. Continuing to climb, the Slugcat is ambushed
by a skilled predator known as the Dropwig, which drags them back to their lair. These insects resemble large earwigs, and
are experts at catching prey. After finding a good hiding spot on the ceiling,
the Dropwig will place bait like spears beneath their perch to lure prey into an ambush. This behavior is an intriguing display of
intelligence, and makes the Dropwig a cunning adversary. At last, you reach the top of the wall. Above the rain clouds for the first time in
the game, itâs a rare peaceful moment... Elsewhere atop the wall, the playerâs Slugcat
encounters a spiritual remnant of an Ancient known as an echo, which tells you the transcendence
youâre looking for is close at hand. The echo says your struggles âcan all fade
like a morning mist beneath the glory of the sun.â By this point in the game, the player has
faced so many dangers that it almost feels like the echo is speaking directly to you. To reach your destination, you must first
brave the dizzying heights of the sky islands. Flying centipedes called Centiwings twist
about in the atmosphere, undaunted by the formidable altitude. Peculiar insects called Noodleflies also buzz
about in this region. Though typically neutral, when threatened
they extend a retractable needle-like tip from their proboscis and attempt to spear
the Slugcat clean through. With Nooodleflies around, it is wise to move
quickly. The Sky Islands lead to the expansive Farm
Arrays, the second-to-last ecosystem before the end. This biosphere is dominated by Worm Grass
â hostile plant-like creatures that attempt to latch on and consume the Slugcat when it
passes by. The best way to cross large fields of Worm
Grass is to hitch a ride on a Rain Deer. These towering lifeforms are the tallest land
animals on Rain World, and are able to step through the carnivorous fields thanks to their
long, powerful legs. Since Rain Deer are one of the few truly peaceful
species you can encounter, thereâs something soothing about their presence⌠At last, the playerâs Slugcat reaches the
dim, dilapidated train-tunnels of the Subterranean ecosystem. The final stop on this great journey, the
region seems grim at first, but eventually, the air begins to glow with a mysterious golden
shimmer, and the shapes of ethereal sea life glimmer in the dark. Some of these environments are truly spectacular
and surreal, with the game squeezing the artistic power out of every last pixel. Eventually, the Slugcat dives into a vast
sea of glowing liquid called Void Fluid, which the game hints is the substance that allowed
the Ancients to ascend. And deep within this iridescent environment,
a final creature is waiting. Coiling in the infinite expanse, the unfathomably
vast Void Worm spirals within the fluid. This creature is by far the single largest
lifeform in Rain World, and seems to call the inky black abyss below the golden sea
its home. A surprisingly inquisitive lifeform, we can
get a glimpse of its surprisingly small head when it comes to investigate the Slugcat. Whether or not the Void Worm is the creator
of the Void Sea or just an inhabitant is unknown, for almost everything about this cosmic creature
and the transcendence itâs home offers is left a mystery. Thereâs a lot of ways to interpret Rain
Worldâs actual ending. On the surface level, you swim into the light
surrounded by other slug cats. Are these members of the family you lost at
the beginning of the game? Are the endless cycles of trials youâve
been through finally coming to a close? Or is none of this even real, and the Void
Sea the Ancients believed offered transcendence really just shows you want it thinks you want? You spend the whole game trying to rise above
the ecosystem, to break out of the food web you find yourself in â but is such a thing
really possible? I wonât give away all my opinions on Rain
Worldâs ending, because I think part of the gameâs power comes from its ability
to be interpreted. In any case, I certainly believe that Rain
World stands out thanks to its incredibly unique and detailed approach to simulating
a virtual biosphere through procedural animation and AI interactions. If youâd like to check it out for yourself,
be aware that it is a brutally challenging game that really makes you feel like youâre
on the bottom of the food chain. Itâs so dense that I couldnât cover everything,
so thereâs lots more to uncover if youâd like to take the plunge yourself⌠As always, thanks for watching. If you enjoyed this entry, please lend your
support by liking, subscribing, and hitting the notification icon to stay up to date on
all things Curious. See you in the next video.
If you like this video, want to know more about the game and the creature AI, I highly recommend this vid: https://www.youtube.com/watch?v=hOsYTzd0yeA
Watched 8 mins then realized I probably want to play this myself, so I'll stop spoiling the creature designs.
The stuff described by this video is really cool, but it feels like they're not so much describing a "complex ecosystem" as just a series of neat creature designs and AI patterns?
love this game more than nothin great video everyone investigate
Beautiful game â thank you for sharing!