There, you play as a slime, which initially has no name, but eventually gets named MO by the narrator: a mysterious female voice that inhabits MO's mind. You need to make your way through a futuristic facility that must have been cutting edge, but has fallen into disrepair long ago, being overrun by both horrific mutants and primitive humanoids referred to as inhabitants. As you go through the game, you collect memory fragments of the voice, which fills in the backstory of the disastrous experiments that led to the current situation.
Compare to Gish by Edmund McMillen.
Tropes present in this game:
- Advancing Boss of Doom: The fifth boss "battle" is a chase sequence from an unnamed dark beast in a nearly monochrome environment, which is vanquished when you finally reach the literal light at the end of the tunnel. It is also very strongly implied to have taken place entirely in your head.
- It is soon followed by another chase sequence against the Inhabitants' huge battle mech. Then, however, MO takes control of a bipedal walker and gets to dish out the pain instead.
- A.I. Is a Crapshoot: Played with. The resident master AI Dylan certainly appears villainous as it both opposes MO and the voice and eliminates the primitive, yet clearly sentient and humanoid Inhabitants with zero regret. However, it turns out that he acts fully in accordance with the instructions that were given to him by the genuinely evil head researcher, and he is justified in trying to prevent the physical reunion of MO and the voice, as that would reactivate the Final Termination Weapon. Once MO realizes the voice's motives, Dylan helps to shut down Final Termination Weapon in the ensuing battle.
- Ambiguous Gender: MO's gender is never given out, but there is evidence for both sides. The Voice calls MO 'little guy' up until giving them a name, but later on it is revealed that MO is a lesser copy of The Voice with some of her memories and uses her voice-sounds when they eventually speak.
- Badass Adorable: The eponymous MO is a cute, adorable blue slime. They are also capable of bounding every which way, smashing through walls and other obstacles, latching onto enemies' heads to control them (and even rip them off!), and they go up against creatures significantly bigger than them.
- Bait-and-Switch Boss: After being defeated for the first time, The King of Inhabitants shows up again, wielding an axe and with a whole group of loyal Inhabitants cheering on him in the background. Then, a giant worm named Doula shows up and immediately consumes it, along with everyone in the background, before the battle proper begins.
- Bittersweet Ending: The good ending. Elara's memories are returned to her, allowing her to be at peace and pass on. However, Dylan is broken during the final battle, MO is left alone, and Jeremiah Greenbell is implied to have escaped.
- Bottomless Magazines: The twin gatling guns of the ancient bipedal mech never run out of bullets, although they do overheat if used too much.
- Breath Weapon: After it hits its head on the crates a couple of times, Doula the Mutated Beast starts attacking with a long stream of acid from its mouth.
- Collision Damage: Doula, the Mutated Beast is so poisonous that touching it is immediately damaging to MO.
- Combat Tentacles: The first boss, The Errors, hangs upside down from the center of the ceiling and attacks with two tentacles hanging from the left and right. You first need to trick it into using these tentacles to destroy several slime-encased corpses around the area, and then a node on its neck, which finally kills it.
- Cooldown Hug: MO gives Elara one before the credits roll. Well, the best slimes can do anyway.
- Turns into a Deadly Hug courtesy of Elara in the bad ending.
- Crate Expectations: Crates play a large role in the Doula battle, as the boss needs to be tricked into headbutting them in order to defeat it.
- Crosshair Aware: Doula regularly goes offscreen, but arrows will show up to indicate where it'll be coming from. If it does an attack where it snakes across the screen, you'll even be briefly shown the entire trajectory!
- David Versus Goliath: While the player character reaches up to an average human's waist, the enemies and bosses are incredibly huge compared to him.
- Deflector Shields: The bipedal combat mech MO takes control of at one point is able to generate a typical blue bubble shield with a beecomb structure around it.
- The Dog Bites Back: The entire game essentially comes down to this as it turns out that the voice guiding MO is that of Elara, a scientist who was turned into a slime creature by the lead researcher Jeremiah Greenbell. This merged her with Extremenergy, and thus she became a power source for the Final Termination Weapon. However, she was beset with the desire for revenge, and so the two other scientists soon realized how dangerous she became and sealed her away. However, this didn't save them from getting killed by Elara's only ally, Sirius, though he also ended up dying himself as the complex was flooded with poison. Much later, Elara learned how to split herself into little pieces, but lost a bit of her memories every time. MO is the latest such piece and her last chance; by the time they emerged, the only thing she remembers is the desire to reach Final Termination Weapon to exact her revenge.
- Enemy Mine: Dylan recovers after its first defeat and eventually helps MO to disable Final Termination Weapon, now commanded by the voice.
- Evil All Along: It eventually turns out that what the voice really meant by freedom was to activate the Final Termination Weapon, and use it for revenge against someone who may have been responsible for her transformation, but who now may not even be alive, or anywhere close to here.
- Floating in a Bubble: MO can hop into massive bubbles that arise from purple Acid Pools. However, MO cannot steer the bubbles in any particular direction, which means that if a bubble is headed towards a spike-filled wall, MO must leap onto another bubble to evade danger.
- Flunky Boss: The Errors regularly drops down a zombie-like humanoid during its battle. However, these tend to get quickly destroyed by its own attacks. If they get impaled by its tentacle, said tentacle is even burdened and slowed down the body's weight: the boss then brings it up to its mouth in order to devour the body from it.
- Friendly Fireproof: Enemies like Inhabitants completely ignore the spikes that are fully lethal to MO.
- Gatling Good: The large bipedal mech that MO eventually takes over has two large rotary cannons in its shoulders, which able to literally blast through entire obstacles in their way.
- Giant Animal Worship: The Inhabitants once had a mutually beneficial relationship with the giant worm Doula, caring for it's eggs as a show of thanks for being 'Mother of the Land' and providing huge quantities of life-giving water. Doula is no longer holding up it's end of the bargain after being experimented on and mutated by human scientists. It continues to lay eggs but the offspring are shown to be mutated and vicious to the inhabitants who still try to look after them.
- Heroic Mime: Being a slime, MO is obviously incapable of speech, so the story is entirely narrated by the voice, and sometimes other characters like the AI Dylan. Until the end, when they, in their ascended state, are able to say "You are wrong, this isn't what you wanted".
- Instant Flight: Just Add Spinning!: The Double Jump is actually MO hovering in the air with rapid spinning. When suspended midair, MO can change the trajectories of their jumps.
- Laser-Guided Amnesia: Played With. MO, as a newly-created being, doesn't know anything at all. The Voice, on the other hand, lost some of her memories creating MO and all the failed attempts that became The Errors. This leaves her, and the player, knowing very little apart from that she needs MO to come help her somehow. Shards of her memories are the games primary collectible.
- Laser Sight: The turrets of the Fatal Trap encounter all have laser sights with very generous aiming interval, in order to compensate for having to dodge six of them at once.
- Multiple Endings: Two endings, one bad and one good, determined by whether or not you collect all of the memory shards.
- If not all memory shards are collected, she is still determined to get revenge one way or another otherwise, even after MO destroyed the weapon and the lifeform, and proceeds to possess MO.
- Doing so, allows the voice to fully remember her past as Elara and to be at peace, passing on and allowing MO to live.
- Names to Run Away from Really Fast: The Final Boss has a fittingly ominous name of Final Termination Weapon. Played with in that her next phase, Extremenergy Life Form, sounds much less threatening, but is far more powerful in comparison.
- Off with His Head!: Doing a Dash Jump when MO is wrapped around a head will rip off the organism's head.
- One-Winged Angel: This occurs during the Final Boss battle, as the voice controlling Final Termination Weapon is still able to evolve into the Extremenergy Life Form that outright breaks free of the facility and blasts off into the stratosphere. Moreover, MO also evolves, absorbing every leftover fragment in order to be able to hover to great heights and do battle in the sky.
- People Puppet: When MO latches onto creatures with heads, he gains access to their thoughts and can manipulate their actions. The resulting "puppets" can perform simple actions such as pressing buttons or pulling levers, but they are unable to attack.
- Rank Scales with Asskicking: The King of the Inhabitants is also their top fighter.
- Shockwave Stomp: Cutscene version: after getting defeated by MO, King of Inhabitants strikes his spear to the ground so hard, it causes the floor collapse, and sends MO into the next area.
- Shout-Out:
- King of Inhabitants' battle has very similar mechanics to that of Hollow Knight's Hornet.
- There's a battle against a tall battle machine of the Inhabitants, which has an electric guitar player on top - just like the famous guitar flamethrower in Mad Max: Fury Road.
- Spikes of Doom:
- Purplish spikes are a frequent obstacle in this game, although they do not affect anyone else. The first boss, The Errors can also generate thick, sharp thorns everywhere but directly beneath him on the floor.
- Notably, King of Inhabitants can climb them with no problem, but they are lethal to you.
- Spread Shot: In the second phase of his battle, DYLAN generates an orb that fires multiple rings of projectiles.
- Super Mode: MO gains one for the final boss. After the voice powers herself up and starts breaking into the stratosphere, they absorb the leftover fragments to transform into an enhanced version of themself. They are able to fly and one-shot the robots the voice sends after them, and break capsules popping up on her coils to absorb her energy and supercharge their dash to deal some major damage on her weakpoint. Naturally they'll need it, considering all the crap she throws at him to try and destroy them.
- Super Spit: The boss worm named Doula gains the ability to spit two-three acid globules in mid-air and have them land at certain spots halfway through the fight. They also leave behind equally damaging pools for a few seconds.
- The flying monsters also have a reddish-brown spit attack.
- Tactical Suicide Boss:
- The Errors would have been invulnerable if it never tried to attack with its tentacles, and instead only tried to spam the thorns on the floor and the acid spit. Instead, you can trick those tentacle attacks into destroying parts of itself.
- King of Inhabitants is way out of MO's reach when he sticks to the spiked ledge. However, he always has not to just go down to the ground, but to over-exert himself there until he has to stay crouched for several seconds to recover, which becomes an opening for MO's strikes time and time again.
- Doula, the Mutated Beast, would have been fine if it wasn't for its fondness for headbutts, as MO is able to use the two buttons in the area to summon crates from an unseen repository above, and bumping into them is the only thing that can damage it. It clearly appears aware of this, too, as it soon learns to spit acid (eventually even growing a second head on its rear end to do the same) specifically at or near the second button, ensuring MO will be hit if you try charging at it too early.
- Too Dumb to Live: Inhabitants are the primitive humanoids living on the planet in question: while some of them know how to operate advanced weapons left behind before the Collapse, most just have throwing spears. Literally dozens of such spear-throwers will stand and attempt to bring down a straight-up bipedal combat mech with gatling guns and laser drones instead of trying to be even remotely reasonable and flee.
- Transformation Horror: Some of the snippets of memory you can get from the chimeras paint a very nasty picture of their transformation into their current forms. It's implied that the process was horribly slow and painful, and that they remained aware of what was happening to them through most it.
- Was Once a Man: Reading the thoughts of the chimeras found in chapter 1 reveals that they are the result of horrifying experiments conducted on human children.
- The voice/Elara used to be a human woman, before Jeremiah Greenbell liquefied her with Extremenergy.
- Wolf Pack Boss: Fatal Trap is mainly a battle with six turrets that are crewed by Inhabitants; however, they also get some assistance from their King after the first two get destroyed.
