drawnso the aliens will be the top layer of the screen figure - shows the first alien on the screen figure - the first alien appears now that the first alien appears correctlywe'll write the code to draw an entire fleet building the alien fleet to draw fleetwe need to figure out how many aliens can fit across the screen and how many rows of aliens can fit down the screen we'll first figure out the horizontal spacing between aliens and create rowthen we'll determine the vertical spacing and create an entire fleet determining how many aliens fit in row to figure out how many aliens fit in rowlet' look at how much horizontal space we have the screen width is stored in ai_settings screen_widthbut we need an empty margin on either side of the screen we'll make this margin the width of one alien because we have two marginsthe available space for aliens is the screen width minus two alien widthsavailable_space_x ai_settings screen_width ( alien_widthaliens