I've been working on the Sopwith game for js13k for a week and am making some progress. I have not been able to allocate the all the time I would like but I have scrolling graphics; a few game objects and a pilotable bi-plane. It has a working keyboard interface and collision detection is working (although I'm not using it currently).
The system is rendering in pure SVG which seems to be working very nicely even when full screen scrolling chrome seem to be hitting 50+ fps.This is the first project I have seriously tried to use SVG and am pleasantly surprised by its flexibility, rendering speed and the general way it can interact with CSS.
Why SVG? I need two different teams using the same graphics with different colour schemes. Additionally I have several requirements to slowly change the appearance of objects to style them in different ways to replicate different era's of computer graphics. The ability to animate line widths, filters and gradients and modify line joins and line endings will all be required to smoothly switch the graphics during game play.
Currently my compressed file size is 3.4kb which I think is okay given that I have the terrain and most of the graphic objects encoded.
Here is a demo version - you can control the cyan plane using the , and . keys to go up and down and the z and x keys to control the speed.