It's a great episode, designed by a variety of different people, and ends up being much better than episodes 2 and 3, though still doesn't reach the peaks of episode 1. Romero, again, is proving to be the most creative level designer on the team. He sets the tone with mission 2, which is possibly the craziest level up to that point. It plays with verticality a lot, and somehow manages to never really make you lament the lack of Y-axis, unlike the latter levels, which often do. Idk if that was Romero's influence, but after mission 2 the verticality games don't stop and kinda become the theme of the episode. Furthermore, thankfully, there are almost no cheap enemy placements and no unavoidable deadly traps.

Overall, I'd say this is probably the most cerebral episode out of the 4. I feel like you end up solving environmental puzzles here a lot more than the previous 3 episodes, and it's surprisingly fun.