button static method
Implementation
static HTMLDivElement button([double opacity = 0.20]) {
enable();
var elem = createDivInline(html: '[>_]');
elem.id = buttonId;
elem.style
..backgroundColor = 'rgba(0,0,0, 0.5)'
..color = 'rgba(0,255,0, 0.5)'
..fontSize = '14px'
..opacity = '$opacity';
elem.onClick.listen((m) => isShowing() ? hide() : show());
return elem;
}