def get_unit(key)
    @values[key] ||= rand
    @values[key] += (rand * (2 * @interval)) - @interval
    @values[key] = 1.0 if @values[key] > 1.0
    @values[key] = 0.0 if @values[key] < 0.0
    @values[key]
  end
def get_unit(key)
    @values[key] ||= rand
    @values[key] += (rand * (2 * @interval)) - @interval
    @values[key] = 1.0 if @values[key] > 1.0
    @values[key] = 0.0 if @values[key] < 0.0
    @values[key]
  end
Takes a hash with all keys supported by Factory, plus these keys and defaults:
  :interval => 0.001
Add a random amount ranging between interval and -1 * interval to the given key's value and return the new value.