Warning: SPOILERS BELOW
Well, one thing I really liked about it was how the eye ball pupils moved with each character.
If I was to pontificate on the meaning, it appears that the player is incomplete in movement (since he can only go right).
When the game starts, one could see the triangle dropping from the sky as possibly a 'soul' entering his self, or some type of category. Then the sign pointing to the right with the exact same symbol is showing his destiny, or path.
Nothing else is shown but nature. A blue sky with clouds and blowing fields of what appears wheat.
Notice he isn't happy until he encounters HER.And when he sees her we see she is blessed with a different symbol and birds flying into the sky as if in celebration. He immediately likes her.
Notice when you walk and stop, his arm immediately goes around her, showing union.
They have mutual likeness of each other and continue to go forward. Again, its the only direction they can go, and now the background graduates from fields to trees. Mature trees.
Notice the last two trees: they form almost a doorway, but more similar to that of a chapel. It's as if these two took their relationship to a point that could be seen as marriage?
Also, notice the trees almost appear to have a human form: two long branches on the side and a middle branch like a head and facing the direction you are walking.
The we come to point in the path where there is a golden door on earth that has a path to the heavens, and only with her symbol.
She proceeds without you and approaches the door and you get a choice: You know what you have to do: Y/N.
What you HAVE to do. Do you HAVE to let her go? And beyond the gate is the same sign that was in the very beginning: your symbol on a pointed sign.
Do you let her go? She doesn't look sad and you are no longer her object of affection: it is whatever awaits above. Clicking yes she fades away happily and your character is again sad, and ALWAYS LOOKING UP.
Then when you reach your sign, you begin to fade away like she did, but 'happily'.
When you say 'No', the opportunity of the gateway disappears, and you get to stay with her, she is now sad and endlessly looking up to what was once there. You are endlessly look at her, sad, almost as if asking 'why do you not want to stay with me'.
When you answer no, you chose your own selfishness to happy above over her happiness, and now no one is happy.
Now you can walk left as well, but now its as if you now dwelling the same area over and over hoping for change or to recapture that first love, but now it's all in vain because the relation is dead due to selfishness.
I dunno. That's my guess. I'm sure i'm reading too much into it!