The Keyboard controls are awkward. K-O-L? Why not J-K-L? Why do I have to shape my fingers into a triangle to be able to shoot/slash/jump awkardly?
The movement is also really stiff and slow. At least let the character run. Maybe more upgrades like more bullets? Faster slashing? It's not too bad. It just needs more work.
Personally it didn't even seem Castlevania like. And Castlevania isn't a "platformer" either it's a metroidvania-esque game.
there is already a control configuration screen, you can configure the controls in the control configuration screen, just click in some key to change it
attack buttons stopped working after first enemy
I really dig the style of the game and your art is really good, there's also a lot of interesting ideas like the mask system, maybe add some more as drops of monsters or something. Still, I feel the game to be really troubled.
My main problem is that the character feels really stiff. First of all because every attack you have has a really big startup, let's compare it to Castlevania since you reference it, Simon's whip does have a delay but the attack happens in about two or three frames, just when you relax your finger after tapping the button, so you aren't stuck in place for too long. The same occurs with the gun, when you shoot you stand there too long and it really dissuades you from using it.
It's also really annoying how you can't jump-attack because it really limits your options and perhaps you could let the player startup the attack mid-air like Castlevania.
¿Podrías agregar algo para hacer más rápido al personaje?, camina demasiado lento.
the game is interesting, and challenging enough. good graphics and music.
the jumps and plataformer bits are a little rough, the jump don't feels right.
the mask mechanics is really fun.
the intro loops.