I liked very much the subtitle - Five Letter Word for "Reality" . An excellent title for this story. I enjoyed your writing style. It's smooth, understandable, simple but effective. There are some really nice paragraphs, which give a strong impact, starting with the first sentence of the story, and then continuing with the setting descriptions which are very effctive and vivid. The premise of the story, although used many times before, is perhaps in these times scarily "disturbing" in the sense of how adequately some of the concepts fit the present day situation - with emphasis on "alone" and closing away from the world and other people.
There's a good tension throughout the story, with rumblings of the siclkings outside, his neighbour and the woman that comes knocking on the door. In all this solving of the puzzle is like that one last resort toward experiencing some normality.As a reader I felt the distress and anguish of your MC, but I really liked how he deals with it. Perhaps some additional, small detail about the MC might make the reader feel even closer to him. The dog certainly adds a lot to the story, the whole setting and even to how we feel about the MC. Both the neighbour and the woman are presented perfectly.
It's an impactful story, especially considering its actuality, it has a great flow and I loved the ending - the punchline of the story defined and realized through solving the puzzle. Great writing!
When a story is so well written, it's impossible not to like it. The detailed descriptions of settings, actions, characters, emotions pull you into the story completely. I enjoyed every chapter, every paragraph actually. It was all so well crafted it was a pleasure to read.