After the failure that Casper had at the simulation room, at the Sgail's Headquarters, he was told to go back home.
That day served for him as a test drive, so his real training would just start the next day. The Sgails also needed to gather some information about him, to know what weaknesses of the soldier needed to be worked on during that week.
It was already night when he returned to his home. Of course, he just noticed it when he got out from the lastest floor of the Castle and went to his own, a residential floor. The artificial lights were very weak, and their shine was the same that the moon projected at night. They couldn't let the floors entirely immersed in darkness, so an illumination like that was needed, otherwise, the citizens would not even be able to walk at night properly.