Update Flat Button Style
Current flat button style is in need of an evolution. Given the current state, the button shows a couple of problems. When hovered, the button shows a ring around the button. In pixel-dense screens this effect can be easily missed. The button doesn't have an easily identifiable area to click or touch.
Current trends from mobile and other systems favor a flat button that is filled when hovered. The most common fill is a darkened gray background. If the button needs to stay selected, the background stays with the button to show the selected state.
Here is an example of what I mean. Notice the hovered buttons.