Mega Tree API

Getting started

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

Prerequisites

You need	Why
.NET SDK 6.0 or newer	Only to build. The mod targets `netstandard2.1`, which is what Mono loads.
BepInEx 5 (Mono build)	Megastore Simulator is a Mono game. The IL2CPP build of BepInEx will not load.
Mega Tree 1.1.0 or newer	The API does not exist in 1.0.x.
A working BepInEx plugin	This page assumes your plugin already loads and logs something.

Mono, not IL2CPP

If your plugin inherits from BasePlugin and overrides Load(), you copied an IL2CPP template - that is Supermarket Simulator, and it will never load here. In Mono the base class is BaseUnityPlugin and the entry point is Awake().

The failure is silent. No error, no log line, nothing in the plugin list. It reads exactly like a broken mod, which is why this is the first thing to check.

Four steps

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

This is one extra reference on top of a normal Mono plugin project, not a replacement for them. You still need BepInEx, 0Harmony, Assembly-CSharp and whichever UnityEngine.* assemblies your code touches - all of them from the game's Managed folder. Project setup has the complete, working csproj.

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

xml

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

Keep MegaTree.xml next to the dll and your editor shows the documentation for every field as you type it. It ships in the same zip.

2. Declare the dependency

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

csharp

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

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.

csharp

private void Awake()
{
    var tree = MegaTreeApi.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) Logger.LogError(handle.Result.ToString());
}

4. Implement the effect

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

csharp

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

One thing that is easier here than in IL2CPP

A Prefix writing to a ref parameter works in Mono. In Supermarket Simulator it installs fine and changes nothing, because the write never reaches the native call - a trap that costs people an afternoon there. Here the assemblies are real IL and the write lands.

Check it worked

Close the game. BepInEx locks the dll while it runs, so a copy over a running game silently fails.
Copy your dll into BepInEx/plugins/.
Start the game, load a save, sit at the store computer and open Mega Tree.
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.

Nothing showed up at all

The Mods tab does not exist until a mod registers something, and an empty sub-tab is never drawn. If every one of your registrations failed, the tab does not appear either - which looks exactly like Mega Tree ignoring you. Check the log before assuming the API is broken.

Common first-run mistakes

Symptom	Cause
Nothing loads, no log line at all	BepInEx 6 instead of 5, or a plugin built against IL2CPP. See Project setup.
`[api] registration of 'X' ... refused - id must be in 'prefix.name' form`	Ids must contain a dot and be lower case. See Registration.
Two Mega Tree versions load	You shipped `MegaTree.dll` with your mod. Set `Private=false`.
`TypeLoadException` on your plugin	The installed Mega Tree is older than 1.1.0.
Node shows but does nothing	You registered it but never wrote the effect. That part is always yours.