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