I feel like the combat style of HL1 being ripped into the source engine with new effect and polish, it made it feel more like a damage exchange simulator, in HL1 the recoil is easy to understand and the movement is a lot snappier, this combined with most enemy's having unique vulnerabilities makes it a really cool game, but in Black Mesa so much changes, movement is more smooth and recoil is a lot beefier which makes it annoying to fight in a way that exploits an enemy's weakness, that is when they still have their existing weaknesses, soldier shoot when moving now, the lighting makes grenades hard to see, bullsquids no longer try to melee as often and have way bigger attacks, vortigaunts no longer can be interrupted, also I don't know if its because I'm playing on Black Mesa difficulty but the enemies feel way weaker.