I am a high-school freshman who is kinda new to Ruby, and I am doing a small project on Ruby.  One of the big things that I want to get out of this project is how to follow the "Ruby standards" that programmers should follow.  Being as new as I am, I have no clue what I should/shouldn't do with this program.  Can anybody tell me what I could do to improve it to fit the community's standards?

    require 'tk'

    $point_A = [0,0]
    $point_B = [750,750]
    $rate = 1.5
    $i=0
    circs=Array.new

    def before_drawing()
	    $point_A = []
	    temp_a = $point_B[0]**1/$rate
	    temp_b = $point_B[1]**1/$rate
        $point_A << temp_a
        $point_A << temp_b
    end

    def after_drawing()
       $point_B = []
       $point_B = $point_A
    end

    canvas = TkCanvas.new(:width=>800, :height=>800).pack('fill' => 'both', 'expand'=>true)

    while $i<10 do
	    before_drawing()
	    circs[$i] = TkcOval.new(canvas, $point_A, $point_B)
	    if $i%2==0 then
		    circs[$i][:fill] = 'blue'
	    else
		    circs[$i][:fill] = 'red'
	    end
	    after_drawing()
	    $i+=1
    end

    Tk.mainloop