(define (make-rectangle-polygon x y width height)
  (list (cons x y)
        (cons (+ x width) y)
        (cons (+ x width) (+ y height))
        (cons x (+ y height))))

(define (make-triangle-polygon x y width height)
  (list (cons x y)
        (cons (+ x (exact (round (/ width 2))))
              (+ y height))
        (cons (- x (exact (round (/ width 2))))
              (+ y height))))

(define (draw-polygon polygon)
  (let* ((first-point #f)
         (previous-point #f))
    (for-each
      (lambda (point)
        (when (not first-point)
          (set! first-point point)
          (set! previous-point first-point))
        (draw-line previous-point point)
        (set! previous-point point))
      polygon)
    (when first-point
      (draw-line previous-point first-point))))

(define (draw-relative-polygon x y polygon)
  (let* ((first-point #f)
         (previous-point #f))
    (for-each
      (lambda (point)
        (when (not first-point)
          (set! first-point point)
          (set! previous-point first-point))
        (draw-line (cons (+ (car previous-point) x)
                         (+ (cdr previous-point) y))
                   (cons (+ (car point) x)
                         (+ (cdr point) y)))
        (set! previous-point point))
      polygon)
    (when first-point
      (draw-line (cons (+ (car previous-point) x)
                       (+ (cdr previous-point) y))
                 (cons (+ (car first-point) x)
                       (+ (cdr first-point) y))))))

(define (move-polygon polygon x y)
  (map (lambda (point)
         (cons (+ (car point) x)
               (+ (cdr point) y)))
       polygon))

(define (rotate-polygon polygon degrees)
  (error "WIP"))