anchor.diff:          | Some vertices -> vertices
           | None -> failwith ("Field vertex index '" + scstring index + "' out of range.")
   
  -    let tryGetFieldDataAtMouse field world =
  +    let tryGetFieldTileDataAtMouse field world =
           let mouseRay = World.getMouseRay3dWorld false world
  -        let (_, _, vertexMap) = getFieldStaticModelAndSizeAndVertexMap field world
  +        let fieldData = getFieldData field world
           let indices = [|0; 1; 2; 0; 2; 3|]
           let intersectionMap =
               Map.map (fun _ vertices ->
  
positive.code: 
          member this.UpdateTime = this.FieldTickTime
  
      let getFieldStaticModelAndSizeAndVertexMap (field : Field) world =
          let fieldModelAssetTag = asset field.FieldTileMap.PackageName (field.FieldTileMap.AssetName + "Model")
          match CachedDescriptors.TryGetValue fieldModelAssetTag with
          | (false, _) ->
              let (_, tileSetsAndImages, tileMap) = World.getTileMapMetadata field.FieldTileMap world
              let tileSets = Array.map fst tileSetsAndImages
  
negative.code:             just world
  
      // here we describe the content of the game
      override this.Content (_, _) =
          [Content.screen Simulants.Default.Screen.Name Vanilla []
              [Content.group Simulants.Default.Group.Name []
                  [Content.light3d Simulants.Light.Name
  