Troubleshooting — documentation

Check which document is running, whether the latest build succeeded and what the first error says. Do not delete caches or reinstall the engine before these checks.

The 3D game window is blank

Run the intended document with F6. F5 may open a different main document.
Check that a Camera3D exists and is Current.
A visible object needs an assigned Mesh. An Entity3D alone draws nothing.
Check the camera position. The first lesson provides values for a cube near the origin.
Check light, Visible and parent objects: a hidden parent can hide descendants.
Read Output and Debugger: a loading error may have prevented required behaviour.

An object visible in the editor may be outside the game camera's view. Editor preview lighting is also separate from game lighting.

The character does not move

Check	What to fix
Input focus	Click the game window
Input Map actions	Match code names exactly, including case and underscores
Script attachment	The file must be assigned to the intended character's Script property
Build	Fix errors, save and rebuild C#
Inspector speed	It must not be `0`
Pause	Stop and restart to rule out accidental pausing

The 3D lesson uses move_forward and move_back; the 2D lesson uses move_up and move_down. These are intentionally chosen action names, not automatic engine commands.

The character falls through the floor

A visible mesh does not create collisions. Both character and floor need CollisionShape3D objects with assigned Shape resources. Use the matching 2D classes in 2D: 2D and 3D physics worlds do not collide with each other.

Check that shapes are enabled, have nonzero sizes and are children of the correct physics bodies. Restore tutorial collision layers and masks to their defaults. Move a CharacterBody with MoveAndSlide() rather than directly replacing Position every frame.

C# will not build

Start with the compiler error pointing to your own .cs file. Common causes:

Message or symptom	Check
Missing `;` or brace	Compare the complete method; inspect the preceding line too
Unknown `Entity3D` or `Reckfell`	`using Reckfell;`, the correct `.csproj` and Reckfell SDK
Missing `partial`	Script classes must use `public partial class`
Duplicate class definition	Two scripts may define the same class name
SDK not found	Complete extraction, the included .NET 10 and matching local package version
Base type does not fit the object	A `CharacterBody3D` script cannot attach to a plain `Entity3D`

File and class names must match in the first lessons. Do not paste a second complete class inside an existing one: replace the file as instructed. Check that your external editor saved changes to disk.

An object is missing or a reference is null

GetEntity paths start at the scripted object. If the camera is under Pivot/Camera3D, Camera3D will not find it. Check names in the local hierarchy and the actual runtime structure.

Find ordinary children in _Ready(), not in field initializers. After an object is deleted with QueueFree(), do not use a stored reference as if it were alive. A NullReferenceException means you should determine which value was missing rather than merely hiding the error.

A C# default does not change the game

Check exported properties in the inspector: saved overrides can differ from script defaults. Check that you are editing the intended instance. Editing the Remote tree during play is not a permanent source-document edit.

For behaviour changes, save C#, stop, build and run again. This rules out an outdated assembly during diagnosis.

A moved asset is missing

Check its new Assets path and asset:// strings in code. The editor updates known resource references, not arbitrary C# path strings. Restore deleted assets from a backup. Use the Assets for future moves.

An export will not open

Match editor and template versions, read the export log and retain all files generated beside the EXE. Check that you used Export Project rather than only a resource package. Repeat the export checks.

Describe a problem effectively

Provide the Reckfell version, Windows version and graphics card, exact first error, running document and short reproduction steps. Include the relevant hierarchy and a small code example. Remove secrets and personal information.