1.Decide on a size for your final ninja star and create 4 straight lines half the decided width, arrange these into a cross

2. Create the center hole using two concentric circles with the ellipse tool

3. Begin using the line tool to draw lines from the far end of the base frame to a point aligned with the smaller base circle.These will serve as the blades

4.Finish the Blades

5. Remove any lines that cross the base circles