things are not quite working yet but here's more descriptive error message for ya

src/net/torvald/terrarum/AppLoader.java

@@ -989,7 +989,7 @@ public class AppLoader implements ApplicationListener {
             return true;
         }
         catch (java.nio.file.NoSuchFileException e) {
-            // write default config to game dir. Call this method again to read config from it.
+            // write default config to game dir. Call th.is method again to read config from it.
             try {
                 createConfigJson();
             }

src/net/torvald/terrarum/IngameInstance.kt

@@ -8,6 +8,7 @@ import net.torvald.terrarum.gameactors.Actor
 import net.torvald.terrarum.gameactors.BlockMarkerActor
 import net.torvald.terrarum.gameitem.ItemID
 import net.torvald.terrarum.gameworld.GameWorld
+import net.torvald.terrarum.modulebasegame.IngameRenderer
 import net.torvald.terrarum.modulebasegame.gameactors.ActorHumanoid
 import net.torvald.terrarum.realestate.LandUtil
 import net.torvald.terrarum.ui.ConsoleWindow
@@ -41,8 +42,8 @@ open class IngameInstance(val batch: SpriteBatch) : Screen {
         set(value) {
             printdbg(this, "Ingame instance ${this.hashCode()}, accepting new world ${value.layerTerrain}; called from")
             printStackTrace(this)
-
             field = value
+            IngameRenderer.setRenderedWorld(value)
         }
     /** how many different planets/stages/etc. are thenre. Whole stages must be manually managed by YOU. */
     var gameworldIndices = ArrayList<Int>()

src/net/torvald/terrarum/gameworld/BlockLayer.kt

@@ -35,37 +35,6 @@ open class BlockLayer(val width: Int, val height: Int) : Disposable {
         data.forEachIndexed { index, byte -> UnsafeHelper.unsafe.putByte(ptr.ptr + index, byte) }
     }
 
-
-    /**
-     * Returns an iterator over blocks of type `Int`.
-     *
-     * @return an Iterator.
-     */
-    fun blocksIterator(): Iterator<Int> {
-        return object : Iterator<Int> {
-
-            private var iteratorCount = 0
-
-            override fun hasNext(): Boolean {
-                return iteratorCount < width * height
-            }
-
-            override fun next(): Int {
-                val y = iteratorCount / width
-                val x = iteratorCount % width
-                // advance counter
-                iteratorCount += 1
-
-                val offset = BYTES_PER_BLOCK * (y * width + x)
-                val lsb = ptr[offset]
-                val msb = ptr[offset + 1]
-
-
-                return lsb.toUint() + msb.toUint().shl(8)
-            }
-        }
-    }
-
     /**
      * Returns an iterator over stored bytes.
      *
@@ -73,17 +42,13 @@ open class BlockLayer(val width: Int, val height: Int) : Disposable {
      */
     fun bytesIterator(): Iterator<Byte> {
         return object : Iterator<Byte> {
-
             private var iteratorCount = 0L
-
             override fun hasNext(): Boolean {
-                return iteratorCount < width * height
+                return iteratorCount < width * height * BYTES_PER_BLOCK
             }
-
             override fun next(): Byte {
                 iteratorCount += 1
-
+                return ptr[iteratorCount - 1]
-                return ptr[iteratorCount]
             }
         }
     }

src/net/torvald/terrarum/gameworld/GameWorld.kt

@@ -222,8 +222,8 @@ class GameWorld : Disposable {
             return tileNumberToNameMap[layerWall.unsafeGetTile(x, y)]!!
         }
         catch (e: NullPointerException) {
-            System.err.println("NPE for wall ${layerWall.unsafeGetTile(x, y)} in ($x, $y)")
+            val msg = "No tile name mapping for wall ${layerWall.unsafeGetTile(x, y)} in ($x, $y)"
-            throw e
+            throw NoSuchElementException(msg)
         }
     }
 
@@ -237,8 +237,8 @@ class GameWorld : Disposable {
             return tileNumberToNameMap[layerTerrain.unsafeGetTile(x, y)]!!
         }
         catch (e: NullPointerException) {
-            System.err.println("NPE for terrain ${layerTerrain.unsafeGetTile(x, y)} in ($x, $y)")
+            val msg = "No tile name mapping for terrain ${layerTerrain.unsafeGetTile(x, y)} in ($x, $y)"
-            throw e
+            throw NoSuchElementException(msg)
         }
     }
 

src/net/torvald/terrarum/modulebasegame/IngameRenderer.kt

@@ -153,11 +153,12 @@ object IngameRenderer : Disposable {
     fun setRenderedWorld(world: GameWorld) {
             try {
                 if (this.world != world) {
-                    printdbg(this, "World change detected -- " +
+//                    printdbg(this, "World change detected -- " +
-                                   "old world: ${this.world.hashCode()}, " +
+//                                   "old world: ${this.world.hashCode()}, " +
-                                   "new world: ${world.hashCode()}")
+//                                   "new world: ${world.hashCode()}")
 
                     // change worlds from internal methods
+                    this.world = world
                     LightmapRenderer.internalSetWorld(world)
                     BlocksDrawer.world = world
                     FeaturesDrawer.world = world
@@ -165,8 +166,6 @@ object IngameRenderer : Disposable {
             }
             catch (e: UninitializedPropertyAccessException) {
                 // new init, do nothing
-            }
-            finally {
                 this.world = world
             }
         }

src/net/torvald/terrarum/serialise/ReadWorld.kt

@@ -1,6 +1,8 @@
 package net.torvald.terrarum.serialise
 
+import net.torvald.terrarum.console.Echo
 import net.torvald.terrarum.gameworld.GameWorld
+import net.torvald.terrarum.modulebasegame.IngameRenderer
 import net.torvald.terrarum.modulebasegame.TerrarumIngame
 import java.io.InputStream
 import java.io.Reader
@@ -22,7 +24,6 @@ open class ReadWorld(val ingame: TerrarumIngame) {
         world.postLoad()
 
         ingame.world = world
-        //ingame.actorNowPlaying?.setPosition(3.0, 3.0)
     }
 
 }

src/net/torvald/terrarum/serialise/WriteWorld.kt

@@ -4,6 +4,7 @@ import com.badlogic.gdx.utils.Json
 import com.badlogic.gdx.utils.JsonReader
 import com.badlogic.gdx.utils.JsonValue
 import com.badlogic.gdx.utils.JsonWriter
+import net.torvald.terrarum.console.EchoError
 import net.torvald.terrarum.gameworld.BlockLayer
 import net.torvald.terrarum.gameworld.WorldTime
 import net.torvald.terrarum.modulebasegame.TerrarumIngame
@@ -43,7 +44,7 @@ open class WriteWorld(val ingame: TerrarumIngame) {
 
     companion object {
         /** dispose of the `offendingObject` after rejection! */
-        class BlockLayerHashMismatchError(val offendingObject: BlockLayer) : Error()
+        class BlockLayerHashMismatchError(val oldHash: String, val newHash: String, val offendingObject: BlockLayer) : Error("Old Hash $oldHash != New Hash $newHash")
 
         private fun Byte.tostr() = this.toInt().and(255).toString(16).padStart(2,'0')
         private val digester = DigestUtils.getSha256Digest()
@@ -80,12 +81,18 @@ open class WriteWorld(val ingame: TerrarumIngame) {
                     //return strToBlockLayer(json.fromJson(type, jsonData.toJson(JsonWriter.OutputType.minimal)) as LayerInfo)
 
                     // full manual
-                    return strToBlockLayer(LayerInfo(
+                    try {
-                            jsonData.getString("h"),
+                        return strToBlockLayer(LayerInfo(
-                            jsonData.getString("b"),
+                                jsonData.getString("h"),
-                            jsonData.getInt("x"),
+                                jsonData.getString("b"),
-                            jsonData.getInt("y")
+                                jsonData.getInt("x"),
-                    ))
+                                jsonData.getInt("y")
+                        ))
+                    }
+                    catch (e: BlockLayerHashMismatchError) {
+                        EchoError(e.message ?: "")
+                        return e.offendingObject
+                    }
                 }
             })
             // WorldTime
@@ -112,10 +119,13 @@ open class WriteWorld(val ingame: TerrarumIngame) {
             val zo = GZIPOutputStream(bo)
 
             // zip
-            b.bytesIterator().forEachRemaining {
+            /*b.bytesIterator().forEachRemaining {
                 zo.write(it.toInt())
             }
-            zo.flush(); zo.close()
+            zo.flush(); zo.close()*/
+            b.bytesIterator().forEachRemaining {
+                bo.write(it.toInt())
+            }
 
             // enascii
             val ba = bo.toByteArray64()
@@ -155,18 +165,19 @@ open class WriteWorld(val ingame: TerrarumIngame) {
             }; Ascii85.decode(buf[0], buf[1], buf[2], buf[3], buf[4]).forEach { unasciidBytes.add(it) }
 
             // unzip
-            val zi = GZIPInputStream(ByteArray64InputStream(unasciidBytes))
+            /*val zi = GZIPInputStream(ByteArray64InputStream(unasciidBytes))
             while (true) {
                 val byte = zi.read()
                 if (byte == -1) break
                 unzipdBytes.add(byte.toByte())
             }
-            zi.close()
+            zi.close()*/
 
             // write to blocklayer and the digester
             digester.reset()
             var writeCursor = 0L
-            unzipdBytes.forEach {
+//            unzipdBytes.forEach {
+            unasciidBytes.forEach {
                 if (writeCursor < layer.ptr.size) {
                     layer.ptr[writeCursor] = it
                     digester.update(it)
@@ -178,7 +189,7 @@ open class WriteWorld(val ingame: TerrarumIngame) {
             val hash = StringBuilder().let { sb -> digester.digest().forEach { sb.append(it.tostr()) }; sb.toString() }
 
             if (hash != layerInfo.h) {
-                throw BlockLayerHashMismatchError(layer)
+                throw BlockLayerHashMismatchError(layerInfo.h, hash, layer)
             }
 
             return layer