def build_base(self):
        """
        create a base random land structure using the AIKIF world model
        """
        #print('Planet ' + self.name + ' has formed!')
        self.world = my_world.World( self.grid_height, self.grid_width, [' ','x','#']) 
        
        perc_land = (self.lava + (self.wind/10) + (self.rain/20) + (self.sun/10))*100
        perc_sea = (100 - perc_land)
        perc_blocked = (self.lava/10)*100
        
        #print('Calculating world : sea=', perc_sea, ' land=', perc_land, ' mountain=', perc_blocked,  )
        self.world.build_random( self.num_seeds, perc_land, perc_sea, perc_blocked)
create a base random land structure using the AIKIF world model