Disco Snake

Wed 15 September 2010 by Jim Purbrick

Rock Band does a great job of inspiring people to play music, can you develop a game that inspires composition? Lumines and Rez create music while you play, can you make games where music creation is the goal, not a side effect? Pictionary does a great job of using game mechanics to overcome creative block, can you use other game-like constraints to inspire creativity? These were among the questions I asked at GameCamp 2 a few months ago and I was keen to explore them at Music Hack Day London a week ago.

The spectrum of potential game-like musical composition tools is huge, ranging from traditional recognisable music interfaces like keyboards and step sequencers at one end, through things that are designed to be both music interfaces and games like Fractal, Rez and Lumines in the middle to things that are recognisably games at the other. While the middle ground is incredibly interesting, 24 hours at a hack day isn’t really long enough to develop a brand new revolutionary hybrid game/music interface, so instead I decided to repurpose an existing game as a sequencer and picked the simplest one I could think of — Snake.

With the interface chosen, the next thing to do was to think about how to map the interface to music composition. The core mechanic in snake is eating food placed on a grid. Grids have a venerable history in music as step sequencer interfaces with time growing form left to right and pitch or samples selected on the y axis. It seemed natural to map food position to note parameters in a similar way. Using the order in which food is selected to determine the order of notes played frees up the X axis to map to a parameter instead of time and also makes playing the game feel more like a progression through a composition: each piece of food adds to the sequence which is continually looping, the music plays and the composition progresses, there is no turning back or revising. By mapping the X axis to velocity pseudo rests can be added to the sequence by selecting food on the left.

Selecting notes requires some deviation from the normal snake mechanics which normally only make a single piece of food available at any time. This restriction would mean that players wouldn’t compose music, simply reveal it as they ate one piece of food at a time. At the other end of the spectrum turning every square in to food would mean that the next selected note would have to be adjacent to the last note, also overly restrictive. Making a limited number of pieces of food available at any time provides a nice middle ground, allowing the player some freedom in the choice of the next note selected, but not total freedom, a restriction which can lead to serendipitous melodies.

The other major mechanic in snake is colliding with your tail, which ends the game, but becomes harder to avoid as you eat food and get longer. One option would be to use that mechanic to intentionally end the game and the composition, but instead I mapped it to sample selection allowing the player to switch between sounds and start a new sequence to build up multi-timbral polyphonic music. By making the world toroidal players can simply let the snake circle around the world when they have finished composing.

A lot of these design decisions came out while implementing the game using processing/processing.js and HTML 5 audio — a technology stack I’d played around with a bit previously, but wanted to explore further. In the end, for this kind of application I don’t think processing brings enough benefit to outweigh the difficulties it adds to debugging. When running on top of Java errors are often reported as mangled Java call stacks and when running in the browser different errors appear as mangled JavaScript. While I can see the attraction to language designers and implementers of building on top of existing technology it often results in having to implement in one language and debug horrible unrecognisable code in another. Incompatibilities are also horrible. With a couple of hours to go I had the entire game running on Java, but was presented with a blank canvas with no useful Firebug errors when I exported to processing.js and having to perform a binary search by commenting out chunks of code to find the error. Not pleasant.

HTML5 audio is also a somewhat fragile technology. Generating an Audio element for each sample playback event leads to current browsers grinding to a halt while resetting and restarting audio elements often causes glitches and delays. Another problem is that JavaScript timers don’t provide enough accuracy for tight sequence playback timing. In the end I rebranded both bugs as features by switching from very transient drum samples which sounded messy to dubby bass and melancholy bell samples that work quite nicely with glitches and unintentionally loose timing.

At 10PM on Saturday night everything had come together enough for me to lose myself in an hour of ambient bleepy electronica and by the time the presentations started at 3PM on Sunday Disco Snake was done.

I’d like to thank all of the organisers and hackers that made Music Hack Day London a wonderful experience and have been pleasantly surprised at the positive reaction that Disco Snake has generated over the last week. The space between music interfaces and games is a very fertile one that I’ll be exploring further in the future and while it’s not there yet, I hope HTML5 audio fulfils its promise of bringing interactive music applications to everyone on the web in the very near future.