It's interesting, couple of things you can fix/change:

1. It's annoying to be asked to provide username every time I complete a level. Can you simply remember my previous choice? Instead something like next level button would be my preference.

2. Tab works until it stops working, it will switch between game elements and then at one point it will focus on buttons (firefox, windows).

1. interesting, I already have something in place for this, it should auto submit after the first time, storing an anonymous userId in cookies. might have been too lax on the browser testing. 2. tab is not a first-class citizen, so your milage may wary :)