>>12147273
HL2 is way too slow to introduce new mechanics and enemies. The devs assume you're retarded and have to ease you into a mechanic over 30 minutes, then change it slightly over the next 30 minutes. By the time the expansions come out they assume you're already familiar with them.
Pic rel gets meme'd a lot, but there's another dev commentary saying that one play tester drowned in a puddle. They're the reason the game is so slow.