Quadtree based collision detection

Use the following controls:

• Cursor keys.

This demo features the following elements:

• Dirty-rectangles based canvas cleaning.
• Built-in key events dispatch.
• Multi key-press mechanishm.
• Character movement in pixels/sec.
• Built-in Quadtree usage.
• Built-in Spatialhash usage.
• Quadtree collision zone identification.
• Spatial Hashmap collision zone identification.