Remembering what was when over 45 episodes spread over years can be rough. Hopefully this will help you out.
Note: Astute gamers may infer spoilers from what is below. Everything is unmarked for ease of reading. You have been warned!Hazard Course
Episode 0: Freeman goes through the training course. Stops at the "Jump to Target" part as he doesn't want to be injured.
Episode 46: Dodges falling debris, avoids landmines, theorizes about alien gravity and the benefits of an extra finger, meets the sniper from Episode 31 again.
Episode 47: Stumbles through the trip-wire maze, shoots an alien weapon dead, laments his inability to hotwire a military vehicle, and gets pinned down by a "tank".
Episode 48: After blowing up the "tank", Freeman plans to become the Lord of War, plays air traffic controller with a rocket launcher, and teaches a guard about the importance of knocking before opening.
Episode 49: Freeman displays his skill in "shotgun chess" amid alien vs soldier combat, considers if he has murdered enough people to alter the course of the timeline, and gets told to put a well placed satchel charge in his pipe and smoke it.
Episode 50: Gordon almost shotguns another security guard, is disappointed in his lack of stamina and self-preservation instinct, and finally uses him as a decoy to escape another Gargantua. He also needs an airstrike map of the whole world.
"Forget About Freeman!"
Episode 51: Freeman laments his One-Man Army status while navigating through Snark mines, only find himself at a dead end.
Episode 52: Gordon ponders if he's taking the longest possible route through the facility while hopping in and out of water, avoiding mines, sharks, and automated guns while he and the military keep each other's life interesting. Also, more rockets, another dead tank, and a suspiciously quiet elevator.
Episode 53: Freeman hopscotches around radiation, finds a tank, and ponders the rarity of stupid aliens in media and the possibility that humanity is just better at invading places, stopping at a hallway full of blood.