IMPORTANT: Modding support is currently highly experimental and driven by community created tools. We are very thankful to the authors of these tools and the players that have shown such passion and dedication in creating mods so far. To show our gratitude we've included some additional functionality in the December 10th update to make their lives a little easier and allow them to reach a larger portion of the community with their creations. However, we cannot currently guarantee any official support or liability for the modding tools themselves or any issues arising due to using community created mods.
Proceed at your own risk.


Background:
Some of you may be familiar with HLMWadExplorer[github.com] by TcT2k. If you are not, here's the gist of it:

HLMWadExplorer has been around for a little while and has been used by the Hotline Miami community to create basic mods for the game. The tool allows you to extract, modify and replace most of the raw data used by Hotline Miami 2 and is most often used to alter the appearance of various elements (sprites and tiles) within the game.

The tool modifies the WAD files that shipped with the game, replacing (some of) the data with custom versions which will then be loaded by the game. While this works it's prone to breaking down when we update the game (Steam will re-download and overwrite the patch WAD file when it changes, causing the player having to re-apply any mods that were in use) and also doesn't really allow level creators to easily ship custom sprites and other assets along with their levels.

In the December 10th update we've added some rudimentary support to make managing community created mods a little easier and allow dedicated content creators to customize the look and feel of their levels and campaigns further by including additional mods that will be used by the game when their levels are being played. Included below is some information on how to author and use this new functionality.

Instructions:
Creating Mods
Use HLMWadExplorer to create a .patchwad file by exporting, editing and replacing assets present in the WADs. Save the file to /My Documents/My Games/HotlineMiami2/mods to have it load throughout the entire game. Alternatively if you want to include a mod only with your custom level or campaign, navigate to the in-game level selection menu and select the campaign or level you wish to include mods for. Press 'O' to show the directory containing the level/campaign files in Windows explorer. Create a mods directory there and save the .patchwad file in this directory. The mods included in this directory will be loaded when playing or editing the level and can be sent to other players as well.

You can also read TcT2k's tutorial here[github.com].

Limitations:

• Mods included with levels or campaigns currently do not support custom sounds. While they can be included in the mod files they will not be loaded by the game as it loads all the audio information once, when the game starts. Mods included in your savegame folder are able to customize sound effects.
  
• Modifying the in-game music tracks is not supported due to legal reasons.
  
• As of right now we are unsure if we can include the functionality as-is for levels distributed on the Steam Workshop. More information on this will be available once the Steam Workshop support is enabled.