Step 32 of Building a Piano says:
Add another @media rule to apply if the browser window is wider than 769px but smaller than 1199px.
The code it accepts as correct includes min-width: 769px and max-width: 1199px. This doesn’t seem to match exactly what the question asks for.
It seems like it should ask for a media rule that applies when the window is 769px and wider, but not when it is wider than 1199px.
Step 27 gives an example with max-width: 960px and describes it as applying when the viewport is 960px wide and below. The code it asks for is a media query that applies when the viewport is 768px wide and below, and max-width: 768px is accepted as correct.
Based on step 27 (and on how min/max width seems to actually work), the min-width: 769px in the accepted answer applies not “if the browser window is wider than 769px”, but when it is 769px wide and wider (and the equivalent for max-width).
It’s possible I’m misunderstanding part of this, but at the very least it seems like step 32 and step 27 contradict each other.
(If the rules added in step 27 and step 32 actually work as they are described in those steps, then the final version of the css has rules for when the window is 768px wide and below, and for when the window is wider than 769px, with no media rule for when the window is 769px exactly.)