A photo editor's button style

I made the rough design as a draft for the demo version of our APP several months ago. I pick vivid colors for the buttons and a subtle gradient for the background, and try to find a visual expression which follows the flat trend, moreover, attracts users to tap.

The pity is that the final piece of the released version is not designed by me (--> http://tu.qq.com/ ). Nevertheless it's actually quite a good photo editor, if you use chinese :)