Hey,
Looking nice, but maybe as Setzer said, increase the size of the signs. I know you are displaying this in 2x, but even at that size they're probably still a bit too small. Remember that the signs/buttons are probably the most important part of your interface - you want people to notice them and click them.
Also, perhaps consider using an extra AA colour for the "JaJitsu" text, some parts are looking extremely jaggy, especially in the Js. Same could go for the clouds too, but I don't think they're as noticeable or important.
Personally, I think the colours could use a bit of work. Currently, it is looking a bit drab and washed out. I've made a colour edit:

In fact, rather than looking at my sloppy colour edit, why not have a look at OwlBoy:
