The plot is completely separate from the of the Mother series, featuring a completely original cast of characters, enemies, and over all plot theme. Not much about it has been revealed, but it stars the young boy by the name of Mitchell, who through a series of unlikely events, is thrust into an underground world in search of his younger brother Chase. There he encounters strange creatures and exotic locations, and gets caught up in the trials and tribulations of this newly discovered realm. The author lists Cave Story, Labyrinth, and Fraggle Rock as some of the inspirations for the story.
The game is notable in that it pushes the EarthBound ROM to its limits, featuring completely new areas, new enemies with incredibly detailed sprites, and several new features not thought possible to pull off in an EarthBound ROM, such as the addition of a Blue Magic system, and having more than four party members that can be swapped out with each other not unlike other RPGs. Attack commands can also have multiple outcomes; for example, Mitch's "taunt" ability will sometimes have him point out the enemies short comings, call them names, or bruise their egos. There are also certain weapons that can use ammo, which is stored in the characters inventory separate from it, such as the staple gun.
As of 2014, the games maps and all the sprites are completely finished, and as of 2015, all the enemies have been properly placed on the maps. HyperBound is now putting the finishing touches on abilities, items, and balance, as well as fine-tuning the game's dialogue. On 6/13/17, a demo was released that covers the first several areas of the game, featuring between one hour to two hours of gameplay. The download for the demo can be found here.
This game contains the following tropes:
- Abandoned Area: There's an abandoned farm just north of Mitch's own farm. The farmer who ran it disappeared sometime before the game's plot kicks off, and it contains the hole that takes Mitch to the underground.
- All Deserts Have Cacti: Even underground ones, apparently. That also walk and attack the party.
- Animate Inanimate Object: The Shameless Plug. It's a living electrical cord!
- Arbitrary Skepticism: Mitch initially refuses to believe ISAAC is a robot, or robots are real, because he's asked Santa for a robot every Christmas and always gets socks instead.
- Beneath the Earth: If what most of the screenshots shown so far and the synopsis of the plot implies, most of the game will take place underground, with occasional breaks to the surface.
- Big Brother Instinct: The plot of the game kicks off when Mitch's little brother Chase goes missing, and he takes it upon himself to find and rescue him.
- Bird People: Wingless, horned version of this trope appear as both enemies and NPCs in the game.
- Black Out Basement: One area of the game is near completely dark cave with only the light of stalagmites illuminating small areas of it.
- Blob Monster: Classical square cube slimes appear as enemies in the game. You can actually see human bones in them from their last meals. There are also grey goop ones in the style of Master Belch from the original game.
- Deadpan Snarker: Mitch. His very first dialogue in the game is poking fun at his brother's made up holiday.
- The Cameo: The Jabberwock enemy is from Jabberwocky.
- Character Name Limits: The dev notes that this was the only thing he flat out couldn't change in one of his updates. As a result, in the game, Mitchell's full name is shortened to 'Mitch' in stuff like stat boxes and such. Characters will still refer to him as Mitchell though, regardless of what names the player puts in.
- The '80s: The period when this game takes place. The dev says one of the main reasons for this is because he wanted to be able to design the robotic characters as what people thought robots would look like in the eighties, and thus wouldn't stand out as much should the game have been set in The New '10s. On top of that, a lot of the character design looks very Eighties-influenced as well.
- Fungus Humongous: An underground area in the game has several gigantic mushrooms strung about.
- Fun with Acronyms: ISAAC stands for Intelligent Search And Assist Construct.
- Ghibli Hills: The game takes place in a more rural setting as opposed to EarthBound. There's still modern houses and roads and such, but generally, there's much more focus on natural forests, and Mitch himself lives on a farm, near other farmers and such.
- Good Morning, Crono: The game starts with Mitch's brother waking him up in the afternoon.
- Mad Scientist: While not much is revealed about him yet, supposedly the games Big Bad will be one.
- Mushroom Man: They guard the games Warp Zones, though they're willing to let Mitch use them without a fight.
- Not a Morning Person: Mitch. He apparently regularly sleeps in.
- Our Monsters Are Weird: Continuing in EarthBound's tradition, quite a few enemies are humorous in concepts, such as their being literal Dust Bunny enemies and walking cacti. However, there do appear to be more conventional enemies too like slimes and such as well. True to what inspired this game and the time period it's set in though, a lot of the monsters and such resemble monster designs and concepts from The '80s.
- Power Copying: The game has a Blue Magic system, which thought to be impossible to hack into the game. Isaac can sometimes copy an opponent's abilities, and gain equivalent PSI abilities in turn. For example, "generate a burst of steam" is the equivalent to PSI Fire Alpha.
- Robot Buddy: ISAAC. Despite being a robot, he's actually the Blue Mage of the group.
- Sarcasm-Blind: Being a robot, ISAAC takes a lot of Mitch's sarcastic comments for face value.
- Self-Deprecation: The game likes to take a lot of shots at itself. One of Mitch's first comments upon getting to the room with broken down robots is that he feels like he's in some bad pulp science-fiction story.
- Shovel Strike: Mitch's first weapon in the game is a shovel.
- Take That!: This game loves poking fun at After School Specials and PSAs, especially the really weird ones.
- Underground City: Several smaller scale underground villages can be found throughout the game, housing the main sentient races of underground.
- Warp Whistle: Sporeways, which can be used to quick travel through the Underworld and beyond.
- When I Was Your Age...: Mitch's day goes into this over how Mitch likes to sleep in, rambling about how he used to get up at four AM to help his father with farm work.
- You Fight Like a Cow: Mitch's taunt command will sometimes have him do this to the enemy, in addition to such things as pointing out the enemies short comings and bruising their egos.