E2M4 now and the vibe is still going strong. This is the first retro game to ever make me want to get as many secrets as possible, not only because of how easy it is to die, but also because there are so many different one-off items that you don't know if you're going to miss something cool. In E2M2, I picked up my first ever bottle of Mana and still have no idea what it does LOL.
Also, the collecting of runes for spells is a simple but great idea: make them effective, even overpowered, in certain situations, but you only can hold a few and you want to hoard as many as possible for the bosses.
Finally, the other thing the game does well is the armour system. Instead of just flat bonuses, you can pick up different grades of armour, some of which add resistance to damage types. That makes you want to avoid getting hit as much as possible, because you don't want to break that Sapphire Platemail that could potentially save your life in levels with lots of cold damage. In trying to avoid getting hit, you're going to have to spend more resources like bear traps and magic runes to take out bigger crowds of enemies. It's just a very smart system.
The more I think about it, the more pissed I am that Arthurian Legends isn't getting the recognition it deserves
