Deadeye is entirely correct here, though you should focus on the sprites for now and worry about overhauling the menu and ui later.
When you do, I have some suggestions:
-Your text is a decent choice, but the gradient boxes detract from it. Get rid of the boxes entirely. Use only the text.
-If you're going to use large gradients, put some use to them. Apply a screen filter to let the stars shine through the black. You can get more creative combining gradients and filters and produce interesting results in relatively little work.
-In images whenever possible, refrain from using pure white. Your planet in the background has a highlight that is far too oversaturated. I think you noticed this too, as you then blurred it. This choice does not fit into the rest of the presentation well.
-Again, whenever possible, try not to commit to large background images - especially ones that may have to be used again elsewhere. The starfield in the back could easily be replaced by a tiled background, and the gradient flares in the corners can be achieved with transparent pngs. In addition, you will benefit from the ability to move, scale, and generally manipulate all these pieces at will.