Controls: (Canvas window has to be in focus)

• Hold the mouse button down in the world to create boxes.
• Press G to show/hide the grid.
• Press R to reset the world.
• Press P to toggle pause.
• When paused you can click on a box to highlight the boxes that will be checked for collision with that box.

The boxes are red when they collide with each other and green if selected.

This is my implementation of a quadtree for collision detection. It is written in Haxe and uses Kha to visualize it.
You can find the source here.