QuadTree implementation with visualization.
Controls:
- LEFT MOUSE CLICK to add rectangles to quad tree.
- HOLD 's' to visualize searching. Default shape is rectangle. HOLD 's' + LEFT SHIFT to change it to circle while searching.
- HOLD 'r' to remove elements from quad tree. Default shape is rectangle. HOLD 'r' + LEFT SHIFT to change it to circle while removing.
- 'd' to toggle debugging of quadtree areas.
- 'x' to reset quad tree.
