Tech Tree API

Getting started

What you need installed, and the shortest path from an empty project to a node on screen.

Prerequisites

Four steps

1. Add TechTree.dll to the references you already have

This is one extra reference on top of a normal IL2CPP plugin project, not a replacement for them. You still need BepInEx.Core, BepInEx.Unity.IL2CPP, 0Harmony, Il2CppInterop.Runtime, Il2Cppmscorlib, Assembly-CSharp and whichever UnityEngine.*Module assemblies your code touches. Project setup has the complete, working csproj.

Download the Tech Tree zip from Nexus, take TechTree.dll out of BepInEx/plugins/rodopoulos/, and add it with Private=false:

<!-- IN ADDITION to your usual BepInEx / Harmony / Assembly-CSharp references. -->
<Reference Include="TechTree">
  <HintPath>C:\...\BepInEx\plugins\rodopoulos\TechTree.dll</HintPath>
  <Private>false</Private>
</Reference>

2. Declare the dependency

Without this attribute BepInEx may load your plugin before Tech Tree, and your registration call would hit a type that has not initialised yet.

[BepInPlugin("BigBoxes", "Big Boxes", "1.0.0")]
[BepInDependency(TechTreeApi.ModGuid)]
public sealed class Plugin : BasePlugin { }

3. Get your module and register

ForPlugin creates your sub-tab inside the Mods tab. The second argument is the label on that sub-tab, and it is the only thing you ever say about where your nodes appear.

public override void Load()
{
    var tree = TechTreeApi.ForPlugin("BigBoxes", "Big Boxes");

    var handle = tree.Register(new UpgradeDefinition
    {
        Id            = "bigboxes.capacity",
        DisplayName   = "Bigger Boxes",
        MaxLevel      = 3,
        BaseCost      = 1500,
        Icon          = UpgradeIcon.Builtin("package"),
        DescribeLevel = lvl => $"+{lvl * 2} items per box",
    });

    // Register never throws. Check the handle instead.
    if (!handle.Success) Log.LogError(handle.Result.ToString());
}

4. Implement the effect

Tech Tree stores the level. Making it mean something is your job. Read the level with TechTreeApi.GetLevel wherever the game asks the question:

[HarmonyPatch(typeof(SomeGameClass), "get_BoxCapacity")]
internal static class BoxCapacityPatch
{
    private static void Postfix(ref int __result)
    {
        int lvl = TechTreeApi.GetLevel("bigboxes.capacity");
        if (lvl > 0) __result += lvl * 2;
    }
}

Check it worked

1. Close the game. BepInEx locks the dll while it runs, so a copy over a running game silently fails.
2. Copy your dll into BepInEx/plugins/.
3. Start the game, load a save, sit at the store computer and open Tech Tree.
4. A Mods tab should be there, with your sub-tab inside it.

If it is not, the log will say why. Open BepInEx/LogOutput.log and search for [api] - every rejection is written there with your plugin guid and the reason.

Common first-run mistakes