The game is a metaphor for growing up, but in a different way than given above
Freud presents the idea of a duality of mind, ego and superego. The ego is, in a sense, the animal mind, the thing that a person is and ought to be. It represents all basal desires, and, through certain extension of reasoning, all greater desires as well. Being that we as a species are symbolic thinkers, one might say the ego is the mental symbol of the self.
However, if the ego were allowed to reign, it would give way to selfishness, and society would crumble; as such, society does not take kindly to the ego, and encourages its members to develop what Freud refers to as a superego. The superego is essentially the ego's abusive parent. Throughout one's life, one is faced with punishment and disdain for doing things that come naturally — the actions of the ego. This punitive disdain is compiled into a symbol: the superego. The superego watches over the ego and basically assaults it whenever it does anything "wrong." This is the source of guilt: the pain experienced by the ego at the hands of the superego.
In that sense, I think the game can be analyzed as follows.
X-1: Childlike hedonism. Every need of the ego is constantly satisfied the moment it arises. This is represented by the relentlessly upbeat music and bright colors. A real-world analogy to this level would be a child playing with blocks and eating sweets.
X-2: Exhaustion/hibernation. The ego is faced with further needs, but the body is too tired to satisfy them, and so goes to sleep. This is represented by the darker colors and happy but more restful music. The sleeping may be represented by the fact that this is the first level where clouds — which might represent dreams — become solid. A real-world analogy to this level would be a child who wants to play more but finds himself too tired and falls asleep.
X-3: Self-pity. The ego has suffered its first injury and realized its mortality. Its possessor likely begins to question his ethics or worth as a human being, but this questioning does not go very deep and likely plateaus around self-pity. This is represented by the still darker colors, the gloomy sprites and tiles, and the music suggestive of active emotional turmoil. A real-world analogy to this level would be a child who has done something wrong while playing and is punished, and thus cries.
X-4: Lethargy. The ego has been mostly silenced by outside forces. Its possessor follows the rules and doesn't do much else. The superego begins to take hold. This is represented by the entirely monochromatic background and tiles and the motionless enemies. The foreboding music represents the gradual introduction of the superego. One might also say that the manner in which this level is entered in world 3, after a sequence of repetitively transitioning between X-1, X-2, and X-3, may represent the cycle of punishments that eventually leads to this level. A real-world analogy to this level would be a late grade schooler who follows instructions without question and doesn't have much fun.
X-5: Questioning. The subject witnesses or experiencing something that reminds him he was once happy. The ego struggles to resurface. Its possessor wonders if he's really living his life or just watching it go by. The struggle is represented by the hands and the fact that the enemies move again. The event that reminds the subject of happiness is represented by how this level is first accessed — by hitting a block in level 1. The wondering is represented by the still creepy but somewhat more complex and interesting music. A real-world analogy to this level would be a middle schooler who one day decides he's fed up with the school structure.
X-6: Rebellion. The ego resurfaces. Its possessor misbehaves on a massive scale. His immediate community does not take kindly to this, especially because the ego's possessor has learned the truths of life and is now dangerous. The resurfacing is represented by the reprise of the music from X-2. The disgust of the community is represented by the faster and more hostile-looking enemies and the spiky plants. The realization of the truths of life is represented by the blood that spews everywhere when you kill stuff or get killed. One might also say that the manner in which one enters this level in world 5 represents a decision-making point; once you question whether you're really enjoying your life, you have the choice either to go back to following the rules without question, thus going nowhere, or to rebel. A real-world analogy to this level would be a teenager being, well, a teenager.
X-7: Repression. After some final punishment or life-changing moment, the superego takes full hold. Its possessor has become a skilled and valuable member of society and is not very much the same person anymore. The final punishment or life-changing moment could be represented by the flash with which this eversion level is introduced. The full hold of the superego is represented by the absence of music. The skill and societal value of the subject is represented by the general difficulty of the worlds in which this level is present. The hands represent the ego trying to speak; the ultimate triumph of Zee Tee over these hands represents that the subject is not listening to it. A real-world analogy to this level would be someone graduating from college and getting a job.
X-8: Ego death. The ego is no more. Its possessor loses all sense of self and becomes nothing more than the disembodied essence of skill, a mindless machine constantly outputting valuable work for no reason. The complete loss of ego is represented by the almost complete absence of color. The mindlessly mechanical nature of the subject is represented by the fact that world 8 is so ridiculously difficult as to disrespect the player, as though whether or not the player was having fun had ceased to be of any significance. A real-world analogy to this level would be a workaholic.
Bad ending: Rejection. The subject finds a mate, but he is not mature enough for her, and she leaves him, thus gravely damaging his ego. The difference in maturity is represented by the princess being a monster, and the grave ego damage is represented by the implication that she kills Zee Tee.
Good ending: Meaningless relationship. The subject finds a mate. They are both mature people. They are not in love, because love is a function of the ego, which they have both lost. They go through the motions anyway because that's what one is supposed to do in such a situation. The mutual maturity is represented by both the princess and Zee Tee being monsters.
Time attack: The endless struggle for acceptance. Preceding death the ego and the superego are supposed to make amends, but since the ego is dead, that has not happened and never will. The subject's final hour fast approaches, and the subject is trying to run away into previous states of psyche because he's not ready to die.
Pulling this:
However, if the ego were allowed to reign, it would give way to selfishness, and society would crumble; as such, society does not take kindly to the ego, and encourages its members to develop what Freud refers to as a superego. The superego is essentially the ego's abusive parent. Throughout one's life, one is faced with punishment and disdain for doing things that come naturally — the actions of the ego. This punitive disdain is compiled into a symbol: the superego. The superego watches over the ego and basically assaults it whenever it does anything "wrong." This is the source of guilt: the pain experienced by the ego at the hands of the superego.
In that sense, I think the game can be analyzed as follows.
Sorry, but having read Freud, it's painfully obvious that that the author of this person only learned about Freud through Pop-Cultural Osmosis: for example, he confuses the id and the ego (which is actually the mediator between the desires of the id and the logic of the Superego), for starters.
Halper's Law: as the length of an online discussion of minority groups increases, the probability of "SJW" or variations being used = 1.