The title of the game, Horror Vacui, means “fear of emptiness”, which might refer to the idea of life being inherently empty and without meaning — which in itself might be a scary thought (and hence good fodder for a horror game) — so we fill it with whatever meaning we can. This alleged lack of meaning might seem nihilistic to some, but I personally see it as a way of saying “make your life count” (which is rather an existentialistic thought than a nihilistic one). You could even say that the meaning of life is to give it meaning (how’s that for a contradiction? (; ).
Horror vacui also happens to be a concept in visual arts, but I don’t think that is particularly relevant to the game, so I won’t go into that: the game’s art style is very minimalistic and pretty far from any “fear of an empty canvas”.
As already said, the game made me think and I like it when a game can do that (it also made we want to know more, which is even better). The creator himself calls it experimental and it is: it really is more about ambience and evoking emotion than anything else, and there is — with one major exception — no sense of agency, which is something I prefer in a game, and also no traditional goal state, so for me it’s more of an experience — albeit a good experience.