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 magic mirror. You move about a grid dodging the boss's attacks while collecting glowing tiles to make progress towards victory. As the fight progresses the boss begins weaving in 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.


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

The boss relies heavily on a custom animation-sequencing system that leverages Bézier curves to get a lot of personality with as little code as possible, whereas the main character uses hand-authored smear frames to get that bouncy movement 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 was the first time I ever composed 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 of code exactly.


Just One Boss traveled pretty far across the internet, getting over a million plays across the many online gaming sites it shows up on.

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 out.