LOGO WebTurtle... draw a half circle at each vertex?

For my college programming class I am having to use Web Turtle. I am trying to draw a spiral like this

I know you must start with drawing a 36 sided polygon like this

SHOWTURTLE
REPEAT 36
  DRAW 10
  RIGHT 10
NEXT

But after that I am lost, I tried this:

SHOWTURTLE
REPEAT 36
  DRAW 10
  RIGHT 10
  GO HALF
NEXT
END


# HALF
  REPEAT 18
    DRAW 10
    RIGHT 10
  NEXT
RETURN 

This results in just a circle over my 36 sided polygon however. I know what I need to do but I cant put into the code. I need to draw a half circle at every vertex of the 36 sided polygon. I don't know why this coming harder to me then JavaScript did! Any tips would be awesome!

So the problem was that I was not rotating the turtle outward before drawing the half circle.Thats why it was just creating a circle over and over. By adding left 180 before drawing the semicircle and then reverting afterwards the problem is fixed.

SHOWTURTLE
COLOR BLUE
THICK 3
LEFT 90
MOVE 140
RIGHT 90
REPEAT 36
   DRAW 10
   RIGHT 10
   GO SEMICIRCLE
   RIGHT 10
   GO REVERT
NEXT
END
END

# SEMICIRCLE
  REPEAT 18
     DRAW 10
     RIGHT 10
  NEXT
RETURN

# REVERT
  LEFT 180
  REPEAT 18
     MOVE 10
     LEFT 10
  NEXT
  RIGHT 180
RETURN