Cosmonaut is a Half-Life Two: Episode Two mod that recreates the style of game-play from the Half-Life series whilst providing a variety of locations to explore as you encounter Combine Soldiers, Antlions, and a wide range of other enemies. The mod sticks to the formula that worked in Half-Life Two in the hope that it is fun to play, and brings about many nostalgic memories.

The mod is set on earth with a very loose premise. You play as a cosmonaut who has had to abandon their space station, but upon arriving back on earth, discover that the place has been overrun by the combine. What happens next? Do you give in to the Combine army, or do you resist and use your skills to find some way of escaping?

The mod was initially made for a mapping challenge that took place on, called NostalgiaVille. After the challenge had been released, the current maps where updated and new maps where created to give some closure to the mod.

To install Cosmonaut you need to -

1.Navigate to the 'Tools' section of your Steam library.

2.Install Source SDK Base 2013 Singleplayer if it has not already been installed.

3.Right click on Source SDK Base 2013 Singleplayer in your Tools list and select “Properties” and then select the BETAS tab. Change it to 'upcoming'.
(If this is the first time you have done this, start Source SDK Base 2013 Singleplayer at least once. )

4. Extract the Cosmonaut_1.0.0 zip file and copy the "Cosmonaut" folder with all the files inside Steam\SteamApps\sourcemods.

5. Restart Steam and when it’s started back up, Cosmonaut should now appear in your list of games.-------------


I post update and developer videos on my YouTube channel so be sure to subscribe for more content relating to Cosmoanut -

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Cosmonaut Updated!

News 1 comment

Wow! What a weekend. It has been incredible to see so many people playing and enjoying Cosmonaut. Thank you to everyone for your kind comments and also your criticism! I would certainly not be able to develop and get better as a level designer if I was not told about the flaws and mistakes that were made.

A lot of the comments I have been getting have been something to the tune of “It’s good, but nothing special” and I wholeheartedly agree with that. I sadly cannot fix that for Cosmonaut as I do not plan on working on it again but I will take everything into consideration when I next make a mod! I am very tired of working on it for now but only because I want to move on and make even more exciting mods. I have however spent the time since release fixing bugs and major issues with the first version. Today, I am rolling out version 1.0.1 which includes a lot of adjustments and changes that make the mod less annoying. You can download the new version here.

Over the past few days, I have had the assistance of Peredice, the project leader over at “Lost Industry 2” who has helped make minor changes and huge optimization adjustments. He helped take a lot of stress off by stepping in and working on the maps for a bit and I am truly thankful that he did. You can view the Lost Industry 2 page here and see all of the amazing things him and his team are doing.


I have made up a change log to document everything that was fixed or updated. I have also put the names of those who either brought the issue to my attention or helped assisting me in updating it. I want to say a huge thank you to those individuals who sent me image logs or video demos so I could quickly and easily fix the issues. This update happened because of you!

Change log


- Heavily optimized the starting area to make frame rates better. (Thanks Peredice)

- Set the starting health value to 35 instead of 34. (Thanks HoodlumScraggy 1)

- Fix an issue when the cops following you would block the door making it never unlock. (Thanks Vizzys)

- Completely overhauled the escape sequence. The player has no risk of being shot while trying to solve the pipe puzzle.

- Removed the torture sounds as there was too much confusion surrounding it.

- Made the wall in the pipe/barrel room thicker and adjusted the lighting origin. (Thanks Eyaura)

- Made the wall in the in vent room thicker. (Thanks Stanley_ros)

- Fixed an instance where metro cops could be seen disappearing from a torture room. (Thanks Lucia)

- Fixed door in that opened too far and clipped the wall.

- Clipped the door in garage that the 2 cops run into as the player could get stuck in there.

- Removed the Easter egg where the player could break the window in the garage.

- Made the elevator drop down water deeper. (Thanks HoodlumScraggy 1)

cosmoanut02 :

- Tweaked generator puzzle to give the player more options. (Thanks Peredice)

- Added an info_lighting to the screens cabinet in the initial rocket screen room. (Thanks Eyaura)

- Removed some props in the first outside section to make movement easier.

- Removed 6th metro cop from the canals section as it was in a silly place!

- The cops in the underground section, behind the blocked up door now walk away once the manhacks have entered the room.

- Removed pallet that obstructed the player’s movement.

- Made the water in pipe puzzle slightly higher and the floor lower to make deeper water.

- Removed creepy invisible dead citizens in super secret vent. (Thanks Lucia)

- Added a few more ammo pickups. (Thanks Vrabo)

cosmoanut03 :

- Added a sound cue to the wooden plank in warehouse as a hint it can be broken. Too many players were backtracking to find barrels to stack.

- Changed the wooden pipe planks to metal in warehouse to avoid confusion.

- Removed the citizens from one train carriage.

- Blocked up stupid looking area making it inaccessible to the player. (Unless they pile up props to get over it.)

- Raised the damage on the electrified water puzzle at the end of the map. (Thanks IMakeLevels)

cosmoanut04 :

- Moved the plug socket above the door to keep environmental continuity. (Thanks Lucia)

- Removed button pressed sound from a pointless decoration button. (Thanks Lucia)

- Removed glitchy melon.

- Made the doors to the health charger and HEV charger room closable.

- Ensured the 2 soldiers having a conversation acknowledge the player when the player moves toward them. (Thanks Strontvlieg)

- Enabled the motion on the dumpsters in the street section.

- Added a railing to the mine elevator. (Thanks Eyaura)

cosmoanut05 :

- Shifted ladder at the start to the middle to accommodate the new railings.

- Made the bar at the first door wooden so it can be punted and broken (Thanks Klems)

- Remove a few lockers that had nothing in them.

- Removed boiler room at bottom of staircase.

- Widened doors during elevator/antlion finale so the antlions can attack the player in the sheds. (Thanks Peredice)

cosmoanut06 :

- Removed some scenery to improve frame rates and heavily optimized the map. (Thanks Peredice)

- Removed wooden crosses from the generator puzzle.

- Made it possible to do the generator puzzle in reverse as I am too lazy to rework it! (Thanks CW3D)

- Fixed buttons on initial elevator having an effect on the assets even when the elevator is moving. (Thanks Lucia)

- Fixed various texture bugs.

- Removed fast zombie from the western warehouse.

- Clipped the infamous “difficult ladder”. (Thanks to everyone who pointed it out)

- Remove "Oliver the Gnome" from conveyor belt. (Thanks Lurker)

- Removed fire from final warehouse as it was not necessary and did not make sense as the character that lit it, got cut a while ago.

- Added blocking damage on the warehouse elevator (Thanks JanKaszanka)

- Remove barnacles for the underground so the mod will no longer crash if the zombie is picked up.


- Fixed various texture bugs.

- Added wall to the end of the sniper bridge so as not to mislead the player.

- Fixed electric puzzle in the final arena where the plug would teleport out of sight of the play in certain areas.

- Added a gate to the bottom of the launch structure so the player does not run up there prematurely. (Thanks Lucia)

All maps:

- Changed some doors that did not open to decoration doors to form consistency. (Thanks Melc311)

- Adjusted the amount of pick-ups in each level to make hard mode harder that is was.

- Tried to give a few hints around the locations of Gnomes.

Once again, if anyone finds all the Gnomes, please post an image of the achievement on twitter so I can see. I have seen a lot of 13 out of 14s but not a full set.

Pretty Pond

So that is all for the moment. After a busy weekend, I will be resting for the next few days. If you find any major bugs, I will try and fix them as soon as possible but I cannot promise a time.

Until next time....


Cosmonaut Released!

Cosmonaut Released!

News 5 comments

It has been a whole year since I initially started working on Cosmonaut. Every week, I have been adding and changing things to make it a fun and enjoyable...

Getting Closer

Getting Closer

News 4 comments

A big thank you to everyone who has shown enthusiasm for Cosmonaut, either on here, on twitter or on the Source Modding Community Discord. I am really...

The Countdown has begun!

The Countdown has begun!

News 2 comments

That’s right! Cosmonauts release is getting closer. This Half-Life 2: Episode 2 mod was made in the style of the Half-Life games with the intention...

This Week In Mods: May 26 2019

This Week In Mods: May 26 2019


The biggest mod stories for the week of May 26 2019.

RSS Files
Latest Release - Cosmonaut 1.0.2

Latest Release - Cosmonaut 1.0.2

Full Version 6 comments

An updated version of Cosmonaut with a few changes.

Cosmonaut 1.0.1

Cosmonaut 1.0.1

Full Version 4 comments

THIS VERSION IS OUTDATED. Please download the latest version. I would like to thank Peredice, the mod leader of "Lost Industry 2" for helping me with...

Cosmonaut 1.0.0

Cosmonaut 1.0.0

Full Version 24 comments

THIS VERSION IS OUTDATED. This is the first Version of Cosmonaut. Cosmonaut 1.0.0

Comments  (0 - 10 of 62)
Guest - - 688,802 comments

I Loved it, 10/10

Reply Good karma Bad karma+1 vote
mizzack - - 3 comments

Such a great mod!

Reply Good karma Bad karma+2 votes
exabyte-worlds - - 67 comments

Отличный мод!
Nice mod!

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tchubbo - - 8 comments

Best hl2 mod i ever played

Reply Good karma Bad karma+3 votes
doitall - - 478 comments

Here a five-part series on this mod, feel free to use the footage for whatever!
Note: this mod is awesome, It feels like it could be it's own Half-Life episode. It demands a download 0-0

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MegaSean45 - - 52 comments

Here's a Gnome Completion vid I made with no walkthrough! Just the gnomes! ^^

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Gideaninja - - 20 comments


cosmonaut 2.5 stars/10 overall, kind of a let down.
much of the mod made little or no sense to me.
much of the maps are clearly lifted from HL2.
At the start, i get why the combine "arrested you"... ok fine. Clearly i was on the run and the intensity had been ramped up. Awesome!

The pipe puzzles were easy enough and some of the others. The trains were fun cuz we all know, Valve loves their trains!!

One Of the THE ODDEST moments was having the citizen purposely run into a nest of hopper mines. WTF was that?
Another odd moment was after liberating the citizens from the local combine grip and setting them free, NOBODY got off the train!??

As the game went made zero sense as to why i was going underground to fight bugs. why i was on the classic indiana jones mine cart ride throughout the tunnels.
Ending up near the launch pad, which you have to be blind, not to see was kind of cool moment.
It got super intense as each part of the rocket launch was completed. However then it dawned on me:
<<They WANT this rocket launched! Why are they trying to kill me for doing what ( as a backstory note ) theyve been planning to do for maybe years??>> JUST MADE ZERO SENSE!

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Vrabo - - 47 comments

The developer has a commentary series on youtube where he explains his thought process. He acknowledges that things don't make sense because it wasn't a priority. Key takeaway is "gameplay/player guidance over realism"

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ilyharaksh - - 26 comments

Hope I will like this mod. Космонавт как никак!

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Guest - - 688,802 comments

Hi, I have enjoyed playing this but am stuck in the space shuttle scene - can't stop the coolant leaking if indeed that is what I am supposed to do - any clues??

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nihilprism - - 5 comments

There's a little rectangular hatch with a handle surrounded by a black and yellow border in the room. if it's flipped over it will look like a rusty sheet of metal a little wider than a suit charger. Just pick it up and place it over the leak!

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