A deep, mysterious and rich game.
Aside from obvious remarks that had been made countless times concerning the game's elegant design and surprising complexity, as well as the atmosphere of indifferent hostility conveyed through the graphics, sound and even control scheme, this game also features some powerful ludonarrative moments.
After "completing" the game several times, it occurred to me that Red is actually stuck in an endless cycle of death and rebirth, and the rogue-like trope of multiple, replayable runs becomes internally contextualized--which is a fancy way of saying: the fact that the players can restart run after run is now a meaningful in-universe mechanic that the character has to face personally.
This is all the more potent considering how this game is an homage to the original Rogue, perhaps even a direct sequel, as some have pointed out.
That combined with other moments where references to cultural elements of yesteryear, like D&D monsters and Tolkien-mythos are realized make for more experiences of mixed nostalgia and discovery. I also remember distinctively that I had a similar sensation to receiving a love-letter when I clicked outside of the game window, intending to quit playing, only to realize that the pause-screen has changed in response to my in-game progression.