yes, it was bittersweet indeed! I felt a deep nostalgia when playing your game. it reminded me of my hometown, of my grandma's cooking, of sundays spent with the family eating at my grandparents' house. it also reminded me of grief, and of how my life was back then, when that person was still around, so back to nostalgia.
I really like the quote you mentioned. “For some reason, the summer evening wind still felt warm.”... as you said, the world still exists and is still beautiful after tragedy. the sky is still blue. the birds still sing. it reminds me of another quote, this one by Robert Frost: "In three words I can sum up everything I’ve learned about life: It goes on."
and definitely consider reading Han Kang. "We Do Not Part" also discusses grief and tragedy, and oddly enough, it also involves someone recovering from an injury at a hospital.