Is flat button with a fill background in-line with material design guidelines

Question

The question is about how that section of material design should be interpreted: http://www.google.co.uk/design/spec/components/buttons.html

If it's basically still fine to have a button with a background which is not elevated but flat. It's not said explicitly in the guidelines that it's a don't but all of the examples show a flat button always as a text button with no background.

When creating a screen with build in keypad (mostly buttons with background fill) it may create to much of visual distraction to elevate them.

Answer 1

A flat button with a fill background doesn't exist in material design, as it goes against the design principles. If you want to have a fill background, then it should be on a raised level to draw attention to it. If it isn't raised, it shouldn't have a fill.

Answer 2

As JohnGB says, the shadow on the button indicates it is a "moving part"...

"The fundamentals of light, surface, and movement are key to conveying how objects move, interact, and exist in space and in relation to each other. Realistic lighting shows seams, divides space, and indicates moving parts."