What is this?
            It's my personal project:
            2D Orthogonal Range Tree Visualization. 
            - The [Input Points and Queries] Canvas: is the canvas
            which holds the points that we are working with.
            
            - The [2D Range Tree] Canvas: displays the orthogonal
            range tree generataed from the points in the [Input Points and
            Queries] Canvas.
          
How to use it?
            1. point inialization:
            - You can enter your own points by clicking on the [Input Points and
            Queries] Canvas.
            
            - Or you can initialize them randomly by clicking the [Randomized 8
            points Points] button. This button can be pressed twice at most (16
            points)
            2. range inialization:
            - You can enter your own range using the four input boxes underneath
            the [Input Points and Queries] Canvas.
            
            - Or you can initialize them randomly by clicking the [Randomized
            Query] button. 
            3. range tree creation:
            - Once you create your points, you can click the [Build Range Tree]
            button 
            4. search:
            - Once you built your range tree, you can click the [Find Points in
            Range] button 
            5. testing:
            - Open the console, and use the multitest(#iterations, #points) to
            test. It would generates random points and compare the result given
            by the range tree with a brute force result.
          
Input Points and Queries
2D Range Tree
Terminologies
            pink nodes:
            visited
            
            S:
            Split nodes
            
            WR & orange nodes:
            Within Range, aka, points that satisfied the constraints
            
            RS & lightgreen nodes:
            Report entire Subtree as found points
            
            lightblue nodes:
            Where we need to do a search in the assoc structure only, but not
            its children