code: func Cover(nextSlide func()) (title string, content tview.Primitive) {
  	// What's the size of the logo?
  	lines := strings.Split(logo, "\n")
  	logoWidth := 0
  	logoHeight := len(lines)
  	for _, line := range lines {
  		if len(line) > logoWidth {
  			logoWidth = len(line)
  		}
  	}
  	logoBox := tview.NewTextView().
  		SetTextColor(tcell.ColorGreen).
  		SetDoneFunc(func(key tcell.Key) {
  			nextSlide()
  		})
  	fmt.Fprint(logoBox, logo)
  
  	// Create a frame for the subtitle and navigation infos.
  	frame := tview.NewFrame(tview.NewBox()).
  		SetBorders(0, 0, 0, 0, 0, 0).
  		AddText(subtitle, true, tview.AlignCenter, tcell.ColorWhite).
  		AddText("", true, tview.AlignCenter, tcell.ColorWhite).
  		AddText(navigation, true, tview.AlignCenter, tcell.ColorDarkMagenta)
  
  	// Create a Flex layout that centers the logo and subtitle.
  	flex := tview.NewFlex().
  		SetDirection(tview.FlexRow).
  		AddItem(tview.NewBox(), 0, 7, false).
  		AddItem(tview.NewFlex().
  			AddItem(tview.NewBox(), 0, 1, false).
  			AddItem(logoBox, logoWidth, 1, true).
  			AddItem(tview.NewBox(), 0, 1, false), logoHeight, 1, true).
  		AddItem(frame, 0, 10, false)
  
  	return "Start", flex
  }
docs: // Cover returns the cover page.