How does The City of Ember meet requirements of a dystopia?

The City of Ember, written by Jeanne DuPrau, illustrates a dystopian society. This is done by DuPrau's use of setting, situations, and character mentality. The setting takes place underground. The power grid and food supply are constantly questioned. The lights flicker and often and blackouts are common. This is dystopic because everyone lives in fear that the power will eventually go out for good. The food supply has dwindled over the years, with certain foods becoming nonexistent. This reduction and loss of food leave characters in fear as well.
Many of the situations depicted in the novel can also be defined as dystopian. No one is able to exert free will when it comes to their occupation. Jobs are drawn from a hat on the last day of school. The outside of the town is considered off-limits, yet some people go there to seek out a better life. Some of those who leave come back insane, which is another reason that inspires fear. Lastly, the timeline for the city is only two hundred years. The city has been going for 240 years, and the population is fearful that the end could come at any time.
One final example of the novel's dystopian characterization is the fear the characters live in. In one event, Doon finds that the mayor has been hoarding and eating the limited food supply. Doon and Lina (the main protagonists) try to warn the other characters about this, and they are threatened by the mayor with their lives.
Most poignantly, the characters live in actual darkness, both physically and mentally—living in fear that the city they reside in may go dark at any time and not knowing they reside in an underground city meant as a way to escape impending doom (it is not told what this disaster is), instead of a city meant to sustain life for generations on end.