# Light metaprogramming.
class Base
  @attr = (name) ->
    @::[name] = (val) ->
      if arguments.length > 0
        @["_#{name}"] = val
      else
        @["_#{name}"]

class Robot extends Base
  @attr 'power'
  @attr 'speed'

robby = new Robot

ok robby.power() is undefined

robby.power 11
robby.speed Infinity

eq robby.power(), 11
eq robby.speed(), Infinity