tank.rb

require 'ruby2d'

set( { :title => "Project", :background => "navy", :width => 640, :height => 640, } )

class Tank
  attr_accessor :x, :y, :width, :height

  def initialize
    @x = (get :width) / 2
    @y = (get :height) / 2
    @width = 50
    @height = 100
  end
end

tank = Image.new('tank.jpeg')
tank.x, tank.y = get(:width) / 2 - tank.width / 2, get(:height) / 2 - tank.height / 2

on :key_held do |event|
  case event.key
  when 'a'
    tank.x -= 3
  when 'd'
    tank.x += 3
  when 'w'
    tank.y -= 3
  when 's'
    tank.y += 3
  end
end

update do
  tank.x
  tank.y
end

show