title: DrRacket On-Key Error/Bug
body: <p>I'm doing a project for my Comp-160 class and my on-key function is doing something odd.</p>
  
  <pre><code>(define (KEY-PRESS W key)
  (cond 
  [(key=? key "left") (make-MOVEB 
                       (- 15 (MOVEB-x W))
                       (MOVEB-y W))]
  
  [(key=? key "right") (make-MOVEB
                        (+ 15 (MOVEB-x W))
                        (MOVEB-y W))]))
  </code></pre>
  
  <p>For context my <code>MOVEB</code> is a structure which holds a position for a bucket to move left and right along the ground level of my scene. When I run this function it let's me move right with no problems but whenever I go left my bucket disappears or moves all the way back to the starting point. </p>
  
  <p>Does anyone have any idea why this is happening? </p>