var square_box_classes = ["square_box-inner-left", "square_box-inner-right", "square_box-inner-top", "square_box-inner-bottom"];

var randomize_square_box = function (elem) {
	var r = Math.floor(Math.random()*4);
	for(i in square_box_classes) {
		if(i != r)
			elem.classList.remove(square_box_classes[i]);
	}
	elem.classList.add(square_box_classes[r]);
}

window.onload = function() {
	for(elem of document.getElementsByClassName("square_box-inner")) {
		var elem = elem;
		randomize_square_box(elem);
	}
};