Very classic Igavania style! I played through the whole thing. The thing that kept me going the most was finding new weapons. That said, it would have been nice to switch between them, rather than it having to be a full replacement. I kind of missed the spear after getting the next one. Maybe they could swap on the shoulder buttons or something similar feeling on keyboard.
I like the sound design, and the music (I even downloaded Genny VST to play around with myself).
The combat encounters I think could use the most work.
Skeleton of Infinity Knifes are rude and i do not like them much. But I realized they were pretty easy to tank. The wizards are just those, but this time they float and can shoot in more than one direction. I think there may be some ways to explore more memorable encounters beyond just, there are more things to fight now. In general, add an attack pattern to any enemy that can keep firing. Even if it's slightly randomized. Having a few attacks to dodge, then a change to get a hit in would be a big improvement. Could have a random roll for like 1 - 3 attacks, iterate a counter, then start an attack delay timer for a couple seconds.
The weapons, while nice to have a variety, did not feel super impactful when the health of the enemies scaled as well. I was taking out the large soldier type enemies in two hits with the spear, got the next weapon, and found the same enemy type was taking 3 hits.
I noticed there was slowdown when loading any of the rooms with lots of enemies, and the transition from one room to the next was near instant. Perhaps adding a short buffer with some fade in would be helpful to hide this.
I was a bit confused at first by the stairs and slopes (I know, especially ironic after what I did in my game...) There were some sections that I could go down like they were slopes, but not up. But the height of each block made it seem like stairs.
I hope I have not piled on too many negatives, really its a group of small nitpicks. I think overall the game has a great unified feel to it, and lots of potential to grow into a great "love letter" of sorts to the Igarashi era castlevanias! If there was more content I absolutely would have kept playing way longer than I did, as I was definitely hooked on finding out what would come next! Great job overall!