QuadTree<E> constructor
Creates a new QuadTree with the specified level and bounds
level - The depth of this quadrant (0 = root)
bounds - The rectangular boundary of this quadrant
Implementation
QuadTree({
required this.level,
required this.bounds,
}) : assert(level >= 0, 'Level must be non-negative'),
assert(bounds.width > 0 && bounds.height > 0,
'Bounds must have positive dimensions') {
_nodes = <Node<E>>[];
}