Thank you for playing, and congratulations on making it to the end! I've shown this game off to quite a few people, and to my knowledge you're the first one that's gotten all the way through. I completely agree that the difficulty is too high. It was a tough balancing act between making the game accessible and creating the type of gameplay I wanted to create, and I think I leaned a little too hard on the challenge. I've had a lot of people suggest reducing the poison damage tick rate even further, and that's something I had toyed with during development, but I was worried that reducing it too much would've impacted the identity of the game. A major factor of what inspired me to make this was the idea of the player being in constant peril with limited resources, and the strategic decisions players would make when put in that situation. I was worried that if the poison ticked down too slowly it would allow the player the maintain their health above 1, which from my perspective would remove the "down to the wire" tension that I was going for. It's a tough call. A part of me wonders if the Zelda-esque format of the game is partially at fault here, and that the way I handled the HP mechanic and the health meter created a false expectation in players. You mentioned that the potions act as little more than short invulnerability timers, and in truth that's actually how I wanted them to work! I know that typically in games of this genre people are used to taking multiple hits and having full access to their health bar, but here it's a bit of an illusion. You have to approach it from a different perspective, but unfortunately that perspective is a little disorientating.
The spikeball enemy could've used a little more visual cues for its attack, yes. Knowing how fragile the main character is, I had tried to give all the enemies deliberate attack patterns that the player could figure out and predict, but on that one I dropped the ball a little. The strategy for the spikeballs is to keep your position in a safe zone until it fires, since when they fire they remain stationary for a couple seconds. As for the room transition damage, that was also an oversight on my part. I knew that with the enemies resetting their positions on room transition that it could lead to the possibility of unavoidable damage. I had tried to leave the entryways clear to prevent this, but it looks like I didn't test that room properly. That's negligence on my part.