anchor.diff:  
   ;;;; Sprites: How do they work?
   
  +(declaim (inline make-sprite))
   (defstruct sprite
     (x           0 :type u8)
     (y           0 :type u8)
  
positive.code: 
  ;;;; Misc Helpers
  
  (defstruct color
    (r 0 :type u8)
    (g 0 :type u8)
    (b 0 :type u8))
  
  (defun get-color (index)
    (let ((start (* index 3)))
      (make-color :r (aref +color-palette+ (+ 2 start))
                  :g (aref +color-palette+ (+ 1 start))
                  :b (aref +color-palette+ (+ 0 start)))))
  
  ;;;; Core
  
  
negative.code: ;;;; TODO: Understand the magic of PPUs. A nightmare of state.
  
  (defvar *resolution* '(:width 256 :height 240) "NES output resolution.")
  (defvar *frame* (make-array 184320 :element-type 'u8) "A single frame to blit.")
  
  (defvar *color-palette*
    #(#x7C #x7C #x7C #x00 #x00 #xFC #x00 #x00 #xBC #x44 #x28 #xBC #x94 #x00 #x84 #xA8
  