     @calculate_projection()
 
     setTimeout (=> @draw_frame()), 150
+
+  calculate_initial_position: ->
+    radian = @angle*Math.PI/180
+    @dx = @force/Math.cos(radian)
+    @dy = @force/Math.sin(radian)
 
   calculate_projection:() ->
     @x += @dx


  draw_banana:(gorilla_x, gorilla_y) ->
    banana = new Banana(@context, gorilla_x+30, gorilla_y-30)
    banana.animate()

class Banana
  constructor:(context, initial_x, initial_y) ->

    @y = 0
    @g = 9.8

  throw:(force, angle) ->
    @force = force
    @angle = angle

    @calculate_initial_position()
    setTimeout (=> @draw_frame()), 150

  draw: ->
