Update step4.html

Author: RodionGork

bunny/step4.html

@@ -30,6 +30,8 @@ <h1>Heeey, I'm Jumping Bunny!</h1>
 
 (define x 0)
 (define y 0)
+(define vx 2)
+(define vy 2)
 
 (define field (getelem "#field"))
 (define fieldW (element-width field))