examples/ex-109.rkt
#lang racket
(require (planet wcy/mpost-wrapper))
(provide main)
(define (main)
  (let* ((u '1cm)
         (a (path (point (op* -1 u) (op* -0.2 u)) '..
                  'tension 1.2 '..
                  (point u (op* -0.2 u)) (dir-spec 'down)))
         (b (rotate 90 a))
         (c (rotate 90 b))
         (d (rotate 90 c)))
    (fill (buildcycle a b c d) #:withcolor (op* 0.8 'white))
    (map draw (list a b c d))))