var dark_tooltip = { 
		style: { background:'#000000',
						 color: '#cccccc',
						 border: {
						 	width: 1,
							radius: 6,
							color: '#000000'
						 },
						 tip: true },
		position: {
			corner: {
			target: 'center',
			tooltip: 'bottomLeft'
			}
		}
};