This class controls the position of the game camera. It is a singleton-type class.
x
the current X position
y
the current Y position
midX
the middle of the screen X position
midY
the middle of the screen Y position
scaleX
the horizontal scale of the display
scaleY
the vertical scale of the display
xMin
the minimum X camera boundary
xMax
the maximum Y camera boundary
yMin
the minimum Y camera boundary
yMax
the maximum Y camera boundary