This guide will show you in details how to earn all 13 achievements in Half-Life 2: Episode One
Watch Your Head, Containment, Elevator Action, Attica!, Escape From City 17 are unlocked by playing through the game normally.
Obviously, I'm not going to make a video walkthrough of the entire game for this one, so I'll just give you a few pointers for each chapter.
Weapons you can use:
Weapons you are not allowed to use:
If you're having trouble in a particular area not developed upon in this guide, maybe the Full walkthrough will help.
If you're really terrified of accidentally firing the wrong weapon, you can (if you're playing on a computer) unbind the 2;3;4; keys and the mouse wheel, leaving you only with your crowbar, gravity gun, rockets and hand-grenades; so you can't switch to a gun by mistake. This is probably overkill, but if you're a fumbler, you might as well try it out.
I suggest you collect all the weapons you find in the game to avoid accidentally using a new weapon when getting auto-switched to it.
If at any point in the game, you fire a shot too many by accident, you can revert to an earlier saved game without invalidating your achievement progress.
Undue Alarm & Direct Intervention:
Obviously, Gordon doesn't even have a gun while he's in the Citadel, so just play normally.
However, remember to start the game from the beginning if you intend to unlock this achievement.
In this chapter, use your Gravity gun to throw heavy, explosive, or flammable objects at zombies. In the dark, remember to shine your flashlight on targets so Alyx can better shoot them down.
Remember that a few direct gravity gun blasts will kill headcrabs.
When you've cleared a room, take a cinder block, heavy piece of rubble or any other efficient gravity gun ammunition with you, this will save you time looking for stuff to throw in your next fight.
If you're taking too much damage, or if Alyx keeps dying, set the game to easy mode, where she is almost invincible.
After the first section of tunnel, Gordon will find a pistol and a shotgun. I advise you to save your game immediately, as this is the point where you get to fire your "one free bullet". The door of the chain-link fence has a padlock on it, so take careful aim and fire ONE pistol round at it, no more, no less. If you somehow manage to miss the padlock, reload your game. Doing so will not invalidate your achievement.
If barnacles grab you from the ceiling, don't panic, shine your flashlight at it and have Alyx save your butt from a painful chomping.
In the multi-storey car lot, when searching for the last car upstairs, use it to crush the Zombine in the room. This will take a few attempts.
Topside, when entering the room full of trip-mines from the streets full of antlions, toss a piece of wood across one of the trip-mine laser beams the Combine are working on.
When Alyx is using the sniper rifle, hang around in the yard until all zombies are dead. If they follow you up the stairs, you might get blocked from both sides, as it takes Alyx quite a while to snipe all zombies on the sky-walk.
Your battle against the antlion guard will be your toughest ordeal. Reload your game if you miss it even once with the explosive barrels, as suitable gravity gun ammunition is very scarce. When all red barrels have hit home, use regular barrels, tires from the APC, but stay away from car wrecks. Also remember to use all your grenades.
If barnacles grab you when Alyx is not around and you are out of SMG grenades and pulse rifle orbs, you're out of luck. Reload an earlier saved game.
Whenever you're fighting soldiers and are unable to find suitable objects to throw at them, duck and hide, let Alyx do the fighting.
During the refugee escort mission, use your rocket launcher liberally since there is an infinite ammunition crate in the parking lot.
The strider fight should pose no problem, all you need ot use are rockets anyway.
As your train rides into the sunset, or wherever, you receive your well-earned achievement.
There! Congratulations! If you played on Steam, you are now a better player than 99.2% or people who have played Half-Life 2: Episode One. (almost 50% of which didn't even finish the game at all, pathetic quitters).
Bravo, citizen! If you followed this guide to the letter, this awaits you in your Steam games library (Providing you're not playing on a console, obviously):
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