Implementation of QuadTree

Controls:
F1: set select mode to 'SelectBox'
F2: set select mode to 'BoxAroundCursor'
F3: set select mode to 'CircleAroundCursor'
F4: spawn random points
F5: clear quadtree
F6: toggle drawing of QuadTree quads
F7: toggle drawing of QuadTree points
F8: toggle drawing of selected points
LeftMouseButton: start of selection
RightMouseButton: push points on the cursor position
MouseWheelScroll: resize select area

Video: https://youtu.be/QHNWJOCjgo0