Really cool concept ! I called it after I beat the third boss, I had all the items and 45 minutes on the clock so I didn't expect to see much more if I kept going. I'm admittedly a picross sicko, but I'm curious to see how you approach difficulty (and the excessive items you receive) if you continue working on this!
The separation of health and the timer feels like it really rigs the game in the player's favor; I'm not sure if your systems would or should accomadate it, but some of the best picross games I've played combine the health and timer, docking more time off the clock for each subsequent mistake. I'm a consummate misclicker so I've found it frustrating in those games, but it also seems like it might be a good fit here.
In any case it's a delightful game, thank you for making it!