In window-mode, the Close/Min/Maximize buttons are inline with the tabs bar.
When maximizing the window to full-screen they disappear. Instead, when moving the mouse to the top of the screen, an additional empty title bar appears with those three buttons.
The window-buttons should either always stay visible and inline with the tabs bar, like Yandex Browser does, or only show up (but still inline with the tabs) when the mouse is moved to the top of the screen. This is how Safari solves this.
The additional title bar should not be displayed.