Our lessons learned: 

1. Create web exports (From our first GWJ). 
2. Test early with a large number of game items that you ultimately intend to have in the shipped game.  Their positioning/sizing isn't that important during development, but the number of items is. It is stressful and hard to diagnose performance issues. (This GWJ).

Another great piece of advice we got from a comment on our submission page is not to use the ESC key for anything when releasing a web export. The ESC key exits full screen when in the browser.

make sure you test your exports