diff --git a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/AbstractSectionLight.kt b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/AbstractSectionLight.kt
index 303a93171..6b961f144 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/AbstractSectionLight.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/AbstractSectionLight.kt
@@ -23,10 +23,12 @@ interface AbstractSectionLight {
 
     operator fun get(position: InSectionPosition): LightLevel
 
+    fun traceFrom(direction: Directions)
     fun traceFrom(position: InSectionPosition, direction: Directions)
 
     fun clear()
     fun propagate()
+    fun calculate()
 
     fun update(array: LightArray)
 
diff --git a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/ChunkLight.kt b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/ChunkLight.kt
index d878d0f87..1ae07350c 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/ChunkLight.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/ChunkLight.kt
@@ -25,6 +25,7 @@ import de.bixilon.minosoft.data.world.chunk.light.section.border.TopSectionLight
 import de.bixilon.minosoft.data.world.chunk.light.types.LightLevel
 import de.bixilon.minosoft.data.world.positions.InChunkPosition
 import de.bixilon.minosoft.data.world.positions.InSectionPosition
+import de.bixilon.minosoft.data.world.positions.SectionHeight
 import de.bixilon.minosoft.gui.rendering.util.VecUtil.inSectionHeight
 import de.bixilon.minosoft.gui.rendering.util.VecUtil.sectionHeight
 import de.bixilon.minosoft.protocol.protocol.ProtocolDefinition.*
@@ -48,11 +49,7 @@ class ChunkLight(val chunk: Chunk) {
         val sectionHeight = position.sectionHeight
         val inSection = position.inSectionPosition
 
-        val light = when (sectionHeight) {
-            chunk.minSection - 1 -> bottom[inSection]
-            chunk.maxSection + 1 -> top[inSection]
-            else -> chunk[sectionHeight]?.light?.get(inSection) ?: LightLevel.EMPTY
-        }
+        val light = chunk.light[sectionHeight]?.get(inSection) ?: LightLevel.EMPTY
 
         if (position.y >= heightmap[position]) {
             return light.with(sky = LightLevel.MAX_LEVEL)
@@ -70,7 +67,7 @@ class ChunkLight(val chunk: Chunk) {
 
     fun calculate() {
         for (section in chunk.sections) {
-            section?.light?.calculateBlocks()
+            section?.light?.calculateBlock()
         }
         calculateSky()
     }
@@ -147,4 +144,10 @@ class ChunkLight(val chunk: Chunk) {
             traceSkyDown(position, maxOf(bottomY, chunk.minSection - 1), topY)
         }
     }
+
+    operator fun get(height: SectionHeight) = when {
+        height < chunk.minSection -> bottom
+        height > chunk.maxSection -> top
+        else -> chunk[height]?.light
+    }
 }
diff --git a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/SectionLight.kt b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/SectionLight.kt
index d6f7924a7..809be9c44 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/SectionLight.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/SectionLight.kt
@@ -13,6 +13,7 @@
 
 package de.bixilon.minosoft.data.world.chunk.light.section
 
+import de.bixilon.kutil.exception.Broken
 import de.bixilon.minosoft.data.Axes
 import de.bixilon.minosoft.data.direction.Directions
 import de.bixilon.minosoft.data.registries.blocks.light.LightProperties
@@ -23,6 +24,7 @@ import de.bixilon.minosoft.data.world.chunk.light.types.LightArray
 import de.bixilon.minosoft.data.world.chunk.light.types.LightLevel
 import de.bixilon.minosoft.data.world.chunk.light.types.LightLevel.Companion.MAX_LEVEL
 import de.bixilon.minosoft.data.world.chunk.update.chunk.SectionLightUpdate
+import de.bixilon.minosoft.data.world.positions.ChunkPosition
 import de.bixilon.minosoft.data.world.positions.InSectionPosition
 import de.bixilon.minosoft.gui.rendering.util.VecUtil.inSectionHeight
 import de.bixilon.minosoft.gui.rendering.util.VecUtil.sectionHeight
@@ -40,7 +42,7 @@ class SectionLight(
 
         when {
             luminance > previousLuminance -> onIncrease(position, luminance)
-            luminance < previousLuminance -> onDecrease(position)
+            luminance < previousLuminance -> onDecrease(position, previousLuminance)
         }
     }
 
@@ -58,6 +60,8 @@ class SectionLight(
 
         if (position.z > 0) traceFrom(position.minusZ(), Directions.NORTH) else getNeighbour(Directions.SOUTH)?.traceFrom(position.with(z = SECTION_MAX_Z), Directions.NORTH)
         if (position.z < SECTION_MAX_Z) traceFrom(position.plusZ(), Directions.SOUTH) else getNeighbour(Directions.NORTH)?.traceFrom(position.with(z = 0), Directions.SOUTH)
+
+        // TODO: This just handles increase in light (i.e. breaking a block), what if a block is placed?
     }
 
     fun onBlockChange(position: InSectionPosition, previous: BlockState?, state: BlockState?) {
@@ -69,8 +73,37 @@ class SectionLight(
         trace(position, LightLevel(block = luminance, sky = this[position].sky), null)
     }
 
-    private fun onDecrease(position: InSectionPosition) {
-        // TODO: Trace until next light increase (or level 0), set all those levels to 0 and then force trace all blocks in range (also from neighbours).
+    private fun onDecrease(position: InSectionPosition, luminance: Int) {
+        // TODO: Optimize (trace in direction and then propagate from edges and trace back again)
+
+        val minX = (position.x - luminance).sectionHeight
+        val maxX = (position.x + luminance).sectionHeight
+
+        val minY = (position.y - luminance).sectionHeight
+        val maxY = (position.y + luminance).sectionHeight
+
+        val minZ = (position.z - luminance).sectionHeight
+        val maxZ = (position.z + luminance).sectionHeight
+
+        for (x in minX..maxX) {
+            for (z in minZ..maxZ) {
+                val chunk = section.chunk.neighbours.traceChunk(ChunkPosition(x, z)) ?: continue
+                for (y in minY..maxY) {
+                    val neighbour = chunk.light[section.height + y] ?: continue
+                    neighbour.clear()
+                }
+            }
+        }
+        for (x in minX..maxX) {
+            for (z in minZ..maxZ) {
+                val chunk = section.chunk.neighbours.traceChunk(ChunkPosition(x, z)) ?: continue
+                for (y in minY..maxY) {
+                    val neighbour = chunk.light[section.height + y] ?: continue
+                    neighbour.propagate()
+                    neighbour.calculate()
+                }
+            }
+        }
     }
 
     private inline fun getOrPut(direction: Directions): SectionLight? {
@@ -231,7 +264,7 @@ class SectionLight(
         event = true
     }
 
-    fun calculateBlocks() {
+    fun calculateBlock() {
         if (section.blocks.isEmpty) return
         val min = section.blocks.minPosition
         val max = section.blocks.maxPosition
@@ -263,12 +296,15 @@ class SectionLight(
         }
     }
 
-    protected fun getNeighbour(direction: Directions): AbstractSectionLight? {
-        return when (direction) {
-            Directions.UP -> if (section.height == section.chunk.maxSection) section.chunk.light.top else section.chunk[section.height + 1]?.light
-            Directions.DOWN -> if (section.height == section.chunk.minSection) section.chunk.light.bottom else section.chunk[section.height - 1]?.light
-            else -> section.chunk.neighbours[direction]?.get(section.height)?.light
-        }
+    override fun calculate() {
+        calculateSky()
+        calculateBlock()
+    }
+
+    protected fun getNeighbour(direction: Directions) = when (direction) {
+        Directions.UP -> if (section.height == section.chunk.maxSection) section.chunk.light.top else section.chunk[section.height + 1]?.light
+        Directions.DOWN -> if (section.height == section.chunk.minSection) section.chunk.light.bottom else section.chunk[section.height - 1]?.light
+        else -> section.chunk.neighbours[direction]?.get(section.height)?.light
     }
 
     private fun propagateVertical() {
@@ -290,23 +326,20 @@ class SectionLight(
         }
     }
 
+    override fun traceFrom(direction: Directions) {
+        if (direction.axis != Axes.Y) Broken()
+        for (xz in 0 until SECTION_WIDTH_X * SECTION_WIDTH_Z) {
+            traceFrom(InSectionPosition(xz), direction)
+        }
+    }
+
     private fun propagateHorizontal() {
         val below = if (section.height == section.chunk.minSection) section.chunk.light.bottom else section.chunk[section.height - 1]?.light
         val above = if (section.height == section.chunk.maxSection) section.chunk.light.top else section.chunk[section.height + 1]?.light
 
         // TODO: merge both?
-        if (below != null) {
-            for (xz in 0 until SECTION_WIDTH_X * SECTION_WIDTH_Z) {
-                val position = InSectionPosition(xz).with(y = SECTION_MAX_Y)
-                below.traceFrom(position, Directions.UP)
-            }
-        }
-        if (above != null) {
-            for (xz in 0 until SECTION_WIDTH_X * SECTION_WIDTH_Z) {
-                val position = InSectionPosition(xz).with(y = 0)
-                above.traceFrom(position, Directions.DOWN)
-            }
-        }
+        below?.traceFrom(Directions.UP)
+        above?.traceFrom(Directions.DOWN)
     }
 
     override fun propagate() {
diff --git a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BorderSectionLight.kt b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BorderSectionLight.kt
index fc43e2bcb..99c602769 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BorderSectionLight.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BorderSectionLight.kt
@@ -107,6 +107,8 @@ abstract class BorderSectionLight(
         return null
     }
 
+    override fun calculate() = Unit // TODO: bottom sky light
+
     protected fun propagateVertical() {
         for (x in 0 until SECTION_MAX_X) {
             chunk.neighbours[Directions.NORTH]?.light?.bottom?.traceFrom(InSectionPosition(x, 0, SECTION_MAX_Z), Directions.SOUTH)
diff --git a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BottomSectionLight.kt b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BottomSectionLight.kt
index c8f1923f2..b00bd8408 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BottomSectionLight.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/BottomSectionLight.kt
@@ -13,6 +13,7 @@
 
 package de.bixilon.minosoft.data.world.chunk.light.section.border
 
+import de.bixilon.kutil.exception.Broken
 import de.bixilon.minosoft.data.direction.Directions
 import de.bixilon.minosoft.data.world.chunk.chunk.Chunk
 import de.bixilon.minosoft.data.world.chunk.light.types.LightArray
@@ -31,6 +32,18 @@ class BottomSectionLight(
 
     override fun Chunk.getBorderLight() = this.light.bottom
 
+    override fun traceFrom(direction: Directions) {
+        if (direction != Directions.UP) Broken()
+        val above = chunk[chunk.minSection]?.light ?: return
+        for (xz in 0 until SECTION_WIDTH_X * SECTION_WIDTH_Z) {
+            val position = InSectionPosition(xz)
+            val current = LightLevel(light[xz])
+            if (current.block <= 1) return
+
+            val next = current.decrease()
+            above.trace(position.with(y = 0), next, Directions.UP)
+        }
+    }
 
     override fun trace(position: InSectionPosition, level: LightLevel) {
         var level = level
diff --git a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/TopSectionLight.kt b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/TopSectionLight.kt
index e8394f375..493eb4ae2 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/TopSectionLight.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/chunk/light/section/border/TopSectionLight.kt
@@ -13,6 +13,7 @@
 
 package de.bixilon.minosoft.data.world.chunk.light.section.border
 
+import de.bixilon.kutil.exception.Broken
 import de.bixilon.minosoft.data.direction.Directions
 import de.bixilon.minosoft.data.world.chunk.chunk.Chunk
 import de.bixilon.minosoft.data.world.chunk.light.types.LightArray
@@ -31,6 +32,19 @@ class TopSectionLight(
 
     override fun Chunk.getBorderLight() = this.light.top
 
+    override fun traceFrom(direction: Directions) {
+        if (direction != Directions.DOWN) Broken()
+        val above = chunk[chunk.maxSection]?.light ?: return
+        for (xz in 0 until SECTION_WIDTH_X * SECTION_WIDTH_Z) {
+            val position = InSectionPosition(xz)
+            val current = LightLevel(light[xz])
+            if (current.block <= 1) return
+
+            val next = current.decrease()
+            above.trace(position.with(y = SECTION_MAX_Y), next, Directions.DOWN)
+        }
+    }
+
     override fun trace(position: InSectionPosition, level: LightLevel) {
         val current = LightLevel(light[position.xz])
         if (current.block >= level.block) return