Swarm Mod wizard complete

You have successfully completed the Alien Swarm mod wizard! The folder you chose to install to now has several sub-folders beneath it:

mapsrc\: For your uncompiled VMF map files.
materialsrc\: For your uncompiled Materials.
modelsrc\: For your uncompiled Models.
src\: The Alien Swarm SDK C++ source code.

Additionally, a folder with your mod's name has been created in <Steam>\steamapps\sourcemods\. This is from where files compiled from the folders above will be loaded, and is all that people playing your mod need.

Setting up the solution

Once it's done copying, go to the location you specified for the mod and go into the src folder.
Go inside the game/server folder and double click on swarm_sdk_server.vcproj. This will load the project into visual studio.
In the solution explorer, right click on solution and choose Add -> Existing project. Add both these projects to your solution:
- game/client/swarm_sdk_client.vcproj
- game/missionchooser/swarm_sdk_missionchooser.vcproj
Do File -> Save All and it will prompt you to save your solution somewhere, e.g. game/mymod.sln

Building and testing your mod

With all the projects added to your solution, you can do:
- Build -> Configuration Manager.
- Select Release. Then press OK.
- Build -> Rebuild Solution. This will make it compile all 3 dlls and copy them to your C:\Program Files (x86)\Steam\steamapps\sourcemods\mymod\bin folder.
Now restart Steam and your mod should appear in your games library.

Setting up Visual Studio for debugging

To run your mod from the debugger:

In Visual Studio, in the Solution Explorer, right click on whichever project is set as your startup project (it will be shown in bold).
Select Properties.
Click Configuration Properties -> Debugging.
In the Command box, enter:

C:\Program Files (x86)\Steam\steamapps\common\alien swarm\swarm.exe

For the Command Arguments:

-sw -dev -game ../../sourcemods/<mymod>

(where "<mymod>" is replaced with your mod name)

For the Working Directory:

C:\Program Files (x86)\Steam\steamapps\common\alien swarm

If you have Steam installed in a different location than "C:\Program Files (x86)\Steam" you will need to adjust the paths accordingly.

You can now press F5 in Visual Studio to build your mod and launch it.

Alien Swarm Documentation

Swarm C++ Code Overview

Swarm Mapping basics

Swarm Campaign Add-on Tutorial

Swarm Objectives

Swarm Overview Map

Swarm Placing Doors

Source SDK Documentation

There are many areas in modding. For a complete overview, visit the main SDK Docs page. Many of these articles were created for the Episode 1 or Orange Box SDK, but they still apply for Alien Swarm. Here are some highlights for beginners:

General advice: From Valve; From other modders
Programming: Choosing a compiler; Your First Entity; Setting up source control
Mapping: Hammer documentation
Modeling & Animation: XSI Mod Tool; Exporting a model; Model Creation Overview
Art & Sound: Material Creation; Soundscripts
Choreography: Choreography creation

Getting help

Help is available from:

The Source SDK FAQ
The Steam User Forums
The hlcoders mailing list and IRC channel (for programmers)
The Noesis Interactive 'Mod Your World' tutorial series (various aspects of Source modding)
The discussion page for each article - like this one's
If you still can't find what you need here, give the Modding Sites section a look.

Good luck!