require 'ruby2d'
set title: '3'
set width:  400
set height: 400
r=12
set background: 'green'
img = Image.new(x:200-r, y:200-r, path:"03.png")

on :key_down do |e|
  case e.key
  when "left"  then
    img.x=img.x-6
  when "right" then
    img.x=img.x+6
  when "up"  then
    img.y=img.y-6
  when "down" then
    img.y=img.y+6
  end
end

show