A little blue character dodges a barrage of attacks from a mirror wearing a top hat. The character managed to collect a glowing tile which fills a bar at the top of the screen.

Just One Boss

Sole developer / Feb 2018


A challenging boss fight against a charming opponent! You move about a grid dodging the boss's attacks all while collecting glowing tiles to make progress towards victory. As the fight progresses the boss begins weaving in even more challenging attacks and mechanics.

The title screen of Just One Boss, some curvy lettering spells out the game's name. Below it the instructions, "Press left to start or right for hard mode".
A frowning mirror boss pounds its knuckles together three times, after which several rainbow-colored after images of the boss appear around it.
A mirror wearing a top hat flings a series of cards at the player, followed by a blue after image doing the same, finishing with a laser attack.


Ever since playing Banana Nababa as a kid I've been a huge fan of boss rushes. So during my three month stay at the Recurse Center (a self-directed retreat for creative programmers) I decided to try my hand at making one!

The boss's relies heavily on a custom animation-sequencing system that leverages Bézier curves to get everything looking and feeling just right, whereas the main character uses hand-authored smear frames to get that bouncy feeling.

The player character from Just One Boss moves one space to the right. A slow-motion version below it showcases the use of smear frames.

Just One Boss marked my first experience ever composing music. I knew nothing going in, but after three weeks of studying music theory I learned enough to be able to compose the game's main chiptune track:

The toughest part of development was figuring out how to fit the entire game within the strict token limit of the PICO-8. I spent a fair amount of time manually compressing the game code and finding ugly tricks to get everything in, and even then the game hits the cap of 8192 tokens exactly.


Just One Boss traveled pretty far across the internet. It's been played over a hundred thousand times on itch.io alone, and it seems like it's probably gotten over a million plays across the many online gaming sites its shown up on.

Just One Boss is most often praised for its brutal difficulty and for the way the audio and the visuals play off of one another.

There's an awesome speedrunning community that tears the game apart, lots of cute Let's Plays on YouTube, many fan games from folks learning programming, and some really heart-warming fan art:

By far the most divisive aspect of the game is a mirroring mechanic introduced halfway through the fight which increases the difficulty significantly. Some players (understandably) find this frustrating and unfair and if I were to do it again I would probably leave it for hard mode.

To everyone who's played Just One Boss: thank you for playing!