function rhombCalc(width, margin) {
	const half = width / 2;
	const mrgnMinHalf = margin - half;
	const halfMinMrgn = half - margin;
	return {
		l: { x: mrgnMinHalf, y: 0 },
		t: { x: 0, y: mrgnMinHalf },
		r: { x: halfMinMrgn, y: 0 },
		b: { x: 0, y: halfMinMrgn }
	};
}
calc square rhomb points by width
origin is in the center of the rhomb
@param {number} width, @param {number} margin
@returns {RhombPoints}