On Sale: GamesAssetsToolsTabletopComics
Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics
SalesBundles
Jobs
Tags

It seems quitting the game during the Game Over screen saved your HP at 0...
I fixed the issue: as soon as the build is up (and it seems to take a bit of time today...), version 1.1.1 will let you reload that save file and have a playable character. Sorry for the inconvenience!

I shall wait for a patch, then!  ^_^

It took a while, but the update is live: https://dreamnoid.itch.io/the-trespasser/devlog/483703/update-111-bugfix-and-hin...

Just gave the boss another go.  I didn't actually have to go back and retrieve any upgrades; once I figured out that the bullets were homing in on me, I found jumping to manipulate their paths was my best bet for dodging.
Finally managed to beat the dude!