The top left corner of the Obeya app on a Mac, before and after, taken from the built app. The dashed blue line marks the bar's middle (29 px from the top), where the bar's buttons, the logo and the pinned navigation's heading are centred. The window's red, yellow and green buttons sat 8 px above it; now they sit on it.
The app drew these pictures itself: the page as the window's web view rendered it, with the window's own buttons from macOS drawn over it at their place. The same build measured the buttons' position at start, at 900×600 and 1700×1100, in fullscreen and after leaving it: always 29 px after the change (21 px before). In fullscreen macOS shows the buttons only in the menu bar that slides in from the top, as for every app.