function dirByAngle(s, e) {
	const rad = Math.atan2(e.y - s.y, e.x - s.x);
	return numInRangeIncludeEnds(rad, -0.8, 0.8)
		? 'left'
		: numInRangeIncludeEnds(rad, 0.8, 2.4)
			? 'top'
			: numInRangeIncludeEnds(rad, 2.4, 3.2) || numInRangeIncludeEnds(rad, -3.2, -2.4) ? 'right' : 'bottom';
}
@param {Point} s, @param {Point} e, @return {Dir}