I'll break it down with as few spoilers as possible.

The world of Hat World is made of worlds made by hats.

Each of these small worlds within it is governed by a hat-wearing "Keeper", reinforcing the concepts that give it substance, and space for non-keepers to reside. Each one has some central theme that sets its the aesthetic, tone, and meaning: The World of Locks, The World of Friends, The World of Despair, just to name a few.

They represent their creator's core values, like a reflection of their inner self, with every part of it an exaggerated aspect of their personality, desires, or innermost thoughts. And of course, they're each full of a crew of fantasy mobs - "Decoys" - that abide by these values and do their Keeper's bidding.

Each of the six protagonists is themselves a Keeper of one of these worlds, and for reasons that run the range from vague to straightforward, they want to take the other hats for themselves by invading other worlds one at a time.

Every one of them has a circumstance that is unique to them, a goal that stands opposed to all the others, righteous or selfish as they come. And while each route bears similarities as the trouble only begins to mount, these circumstances unfold and snowball in wildly different directions.

And as you go through each one, you find answers to some questions you might not have asked, and questions that might only be answered in another story.

Laid-back, dorky, sometimes comically aggressive.

The main six protagonists are dedicated to their goals, and achieve it through their own unique brands of forcefulness (usually). The world they live in is no stranger to casual violence, and nearly all of them are ready to throw hands at the slightest provocation. It's not unlike Touhou, if you're familiar - and not just because of the funny hats.

Even despite some minor aspects of the narrative having the same basic progression on any route, each protagonist's unique mannerisms set them on opposing ends of a wide spectrum of character archetypes. It keeps each of their stories interesting during the common parts, and lets them really shine when it matters.

And besides them of course, there's a regular cast of side characters and party members that have fun interactions every step of the way. You'll meet the likes of a blushing shrine maiden, an archetypical tsundere, and an isekai schoolgirl, and those are just among the playable characters! Despite the variety, most of the entire cast have history together and are on relatively amicable terms, making what you have to do really feel like rocking the boat despite the very sparse upfront context.

Also yeah okay I'll say it. This game has soft yuri written all over it.

This is very important but I'm not good at describing that sort of thing!

At its core, the game is classic turn-based combat, where the player party and enemy commit their actions and then act in a determined order.

Characters (and enemies!) acting in sequence can combo attack under the right conditions, and action order itself can be manipulated through varioustime meansmagic.

Boss encounters often rely on knowing or reacting to what's coming next, or finding the right balance of offense and survival, and the boss design really doesn't pull its punches when it counts.

Stats and skills progress through natural action - melee attacks raise your STR, magic attacks raise your MAG, but your weapon or element of choice also raises your affinity and might teach you new skills. It's designed in such a way that a character will grow into the role you give them, automatically - and even if you build "wrong", there's a curve to playing "catch-up" that doesn't punish your decisions for very long. More open-ended is the Gem system, a shared-resource character skill tree for passives and proficiencies, letting you swap them around freely depending on what you need.

Automatic growth that plateaus based on encounter difficulty does mean that attempts to brute-force grind can be difficult on a first run, but I never personally found the power scaling to be unreasonable. The true difficulty comes in creative boss fight mechanics, which require another level of strategy other than brute force.

To that end, while I never felt frustrated by the raw numbers, it wasn't always enough to just attack and react with the same tried tactics. I never felt that you could truly get softlocked/walled, despite this.

Outside of combat, it's a 2D map-exploration sidescroller, with minor platforming in certain areas. There's lots of map secrets to be found, and more sidequests that unlock upon each stage completion that flesh out little stories (or sometimes just gags) throughout the worlds. Dialogue and hints will always point you in the right general direction, and there isn't anything truly "missable", so it's a low-stress bonus experience to do at your own pace.

Overall, a single full route from scratch, storyline-only, can be as low as a good 10 hours. Although, there's more to this I could elaborate on...