@[email protected] You say it's obvious, but the first time I played Portal 2, I was rushing to finish it and wasn't listening to the Cave Johnson dialog closely, didn't put two and two together that portal paint was made with moon dust, and at the end of the final boss, I hesitated long enough before figuring out that I was supposed to shoot the moon that any tension in that moment was ruined as the game just sat and waited for me.