Rectangle from Vec2.
var Rec2 = require('rec2')
var r = new Rec2(0, 0, 100, 100) //x, y, width, height
//r is a subclass of Vec2, but with
//a .size property (a Vec2)
//and a bounds property a vec2.
//.bounds is the absolute position of the other corner.
create a Rec2
instance with given dimensions.
all dimensions default to 0.
If size must >= 0 or an error will be thrown.
return true if the given point is within the rectangle.
returns true if the given rectangle intersects with this rectangle.
returns the area of the rectangle.
MIT