Clearly the central theme of this story is the way in which we all go through a stage where, like Ravi, we realise our own insignificance and thus undergo a kind of death in terms of our innocence and our hopes which ends our childhood. This is of course highlighted by the funereal game that the other children are playing at the end of the story and in which Ravi refuses to participate. Note how the story ends as Ravi struggles and grapples with what he has learnt from being ignored:
The ignominy of being forgotten--how could he fact it? He felt his heart go heavy and ache inside him unbearably. He lay down full length on the damp grass, crushing his face into it, no longer crying, silenced by a terrible sense of his insignificance.
This is the true theme of this short story as it focuses on growing up and key moments that form a part of that process and teach us of our own "insignificance." The title is related to this theme through the association of the word "twilight," which we think of as being the death of the day. Likewise, "games" is a word that brings to mind competition and struggle and the need to learn the "rules" of life in order to live it successfully.