I eventually beat the game but I won't try New Game +, 300 was hard enough ;).
In practice you effectively have only 2 days as you can't sell after the 3rd one right? Also I think inventory is broken after you sell any item, or something like that, so you can't really buy any medkit I think, but maybe it's a bit more complicated. That's OK, overall these things do not really prevent from playing the game as intended and reach the end anyway.
Overall the game is fun, I like the turn-based gameplay which plays as fast as you press the buttons. The 300 threshold feels right, that was hard but not unreachable, an appropriate challenge which will take me a few retries really adds to the fun of playing a small game to me so that was a plus, I enjoyed learning some efficient routes through the levels. I like the enemy's animations as well.
This is a cool entry, thanks for sharing.