It's easy to understand why Doom became such an influential and iconic game. It's action holds up decades later, and its visuals have aged gracefully into being cartoony fun. Its first episodes are a great opening for what Doom can be, with a good mix of action packed tech bases and puzzle hunts, however I feel that Doom is held back by its later episodes which become a lot more gimmicky, brutal, or sloggish. Some levels in later episodes would leave me wandering for ages. I had killed all of the demons, but because I couldn't pin down some obtuse and poorly hidden key, I was stuck. However, these episodes can only hold Doom back so much, and overall the game outshines it weaker moments, laying out an iconic groundwork for future games and modders to play with.