function addToQuadTree(tree, entity)
{
	if(!rectCollidesRect(tree.pos, tree.size, entity.pos, entity.size)) {
		return false;
	}
	if(tree.elements.length < tree.capacity) {
		tree.elements.push(entity);
		return true;
	}
	else {
		if(!tree.children) {
			tree.children = [];
			let child0 = new QuadTree(); 
			let child1 = new QuadTree();
			let child2 = new QuadTree();
			let child3 = new QuadTree();

			child0.pos.x = tree.pos.x;
			child0.pos.y = tree.pos.y;
			child0.pos.size.x = tree.size.x / 2;
			child0.pos.size.y = tree.size.y / 2;

			child1.pos.x = tree.pos.x + tree.size.x / 2;
			child1.pos.y = tree.pos.y;
			child1.pos.size.x = tree.size.x / 2;
			child1.pos.size.y = tree.size.y / 2;

			child2.pos.x = tree.pos.x;
			child2.pos.y = tree.pos.y + tree.size.y / 2;
			child2.pos.size.x = tree.size.x / 2;
			child2.pos.size.y = tree.size.y / 2;

			child3.pos.x = tree.pos.x + tree.size.x / 2;
			child3.pos.y = tree.pos.y + tree.size.y / 2;
			child3.pos.size.x = tree.size.x / 2;
			child3.pos.size.y = tree.size.y / 2;

			tree.children.push(child0);
			tree.children.push(child1);
			tree.children.push(child2);
			tree.children.push(child3);
		}
		for(let i = 0; i < 4; i += 1) {
			if(addToQuadTree(tree.children[i], entity)) {
				return true;
			}
		}
	}
	return false;
}