This is a full reimagining of the first NES Castlevania in the DOOM engine. The whip is like a short-range shotgun, and you're whipping candles to get hearts. In traditional Castlevania style, hearts are used for subweapon ammunition. The subweapons themselves are reimagined in fun ways: the knife is a 3 knife shot in a horizontal spread, the combat cross bounces on walls, which enables you to shoot enemies around corners, and the holy water makes a damaging puddle on the ground.
I played the first level, and it seems like Batandy made the whole damn game in DOOM form. Very cool. I'm playing in GZDoom, a very nice and flexible Doom engine reimplementation that supposedly is compatible with almost everything made in the original Doom engine.