diff --git a/src/level/blockExt.ts b/src/level/blockExt.ts
new file mode 100644
index 0000000..e2fc73b
--- /dev/null
+++ b/src/level/blockExt.ts
@@ -0,0 +1,73 @@
+import type { NoiseFunction2D } from 'simplex-noise'
+import {blockTypes as T, level as L, probability as P, type Block} from './def'
+
+function trees(r: number, i: number, row: Block[], previousRow: Block[]) {
+  const max = row.length - 1
+  const h = i - 1
+  const j = i + 1
+
+  if (row[i] === T.treeTopMiddle) {
+    if (i) {
+      if (row[h] === T.treeTopRight) row[h] = T.treeTopLeftMixed
+      else row[h] = T.treeTopLeft
+    }
+    if (i < max) row[j] = T.treeTopRight
+
+  } else if (previousRow[i] === T.treeTopMiddle) {
+    row[i] = T.treeCrownMiddle
+    if (i) {
+      if (row[h] === T.treeCrownRight) row[h] = T.treeCrownLeftMixed
+      else row[h] = T.treeCrownLeft
+    }
+    if (i < max) row[j] = T.treeCrownRight
+  } else if (previousRow[i] === T.treeCrownMiddle) {
+    row[i] = T.treeTrunkMiddle
+    if (i) {
+      if (row[h] === T.treeTrunkRight) row[h] = T.treeTrunkLeftMixed
+      else row[h] = T.treeTrunkLeft
+    }
+    if (i < max) row[j] = T.treeTrunkRight
+  } else if (previousRow[i] === T.treeTrunkMiddle) {
+    row[i] = T.treeRootMiddle
+    if (i) {
+      if (row[h] === T.treeRootRight) row[h] = T.treeRootLeftMixed
+      else row[h] = T.treeRootLeft
+    }
+    if (i < max) row[j] = T.treeRootRight
+  }
+}
+
+function ground(r: number, i: number, row: Block[], previousRow: Block[]) {
+  const rootParts = [T.treeRootLeft, T.treeRootMiddle, T.treeRootRight]
+  const prevBlock = previousRow[i]
+
+  if (prevBlock === T.air) {
+    if (r < P.soilHole) row[i] = T.air
+    else if (row[i] === T.soil) row[i] = T.grass
+  } else if (rootParts.indexOf(prevBlock) >= 0) {
+    if (row[i] === T.soil) row[i] = T.grass
+  }
+}
+
+function rock(r: number, i: number, row: Block[], previousRow: Block[]) {
+  if (previousRow[i] === T.soil && r < P.fray) row[i] = T.soil
+}
+
+function underground(r: number, i: number, row: Block[], previousRow: Block[]) {
+  if (previousRow[i] === T.stone && r < P.fray) row[i] = T.stone
+}
+
+export default function createBlockExtender(rand: NoiseFunction2D) {
+  function extendBlocks(level: number, column: number, row: Block[], previousRow: Block[]) {
+    for (let i = 0; i < row.length; i++) {
+      const r = rand(level, column + i)
+
+      if (level < L.ground) trees(r, i, row, previousRow)
+      else if (level < L.rock) ground(r, i, row, previousRow)
+      else if (level < L.underground) rock(r, i, row, previousRow)
+      else underground(r, i, row, previousRow)
+    }
+  }
+
+  return extendBlocks
+}
diff --git a/src/level/blockGen.ts b/src/level/blockGen.ts
index 4315df8..f7c27b9 100644
--- a/src/level/blockGen.ts
+++ b/src/level/blockGen.ts
@@ -1,9 +1,7 @@
 import type { NoiseFunction2D } from 'simplex-noise'
 import {blockTypes as T, level as L, probability as P, type Block} from './def'
 
-export default function createBlockGenerator(noise2D: NoiseFunction2D) {
-  const rand: NoiseFunction2D = (x, y) => 0.5 + 0.5 * noise2D(x, y)
-
+export default function createBlockGenerator(rand: NoiseFunction2D) {
   // randomly generate a block
   // level: number, smaller is "higher"
   // column: number, the x-axis
diff --git a/src/level/index.ts b/src/level/index.ts
index 6f54946..5efc75d 100644
--- a/src/level/index.ts
+++ b/src/level/index.ts
@@ -1,18 +1,18 @@
 import alea from 'alea'
-import { createNoise2D } from 'simplex-noise'
+import { createNoise2D, type NoiseFunction2D } from 'simplex-noise'
 import createBlockGenerator from './blockGen'
+import createBlockExtender from './blockExt'
 
 import {blockTypes as T, level as L, type Block} from './def'
-//import BlockGen from './first-iteration'
-//import BlockExt from './second-iteration'
-//import PlayerChanges from './third-iteration'
 
 export default function createLevel(width: number, height: number, seed = 'very random seed') {
   const prng = alea(seed)
   const noise2D = createNoise2D(prng)
+  const rand: NoiseFunction2D = (x, y) => 0.5 + 0.5 * noise2D(x, y)
 
   const _grid: Block[][] = new Array(height)
-  const blockGen = createBlockGenerator(noise2D)
+  const blockGen = createBlockGenerator(rand)
+  const blockExt = createBlockExtender(rand)
 
   // Apply changes, coming from the player (tocktocktock-plopp!)
   function change (level: number, column: number, newBlock: Block) {
@@ -26,6 +26,7 @@ export default function createLevel(width: number, height: number, seed = 'very
       const previousRow = i ? _grid[i-1] : [] as Block[]
 
       blockGen(level, column, row, previousRow)
+      blockExt(level, column, row, previousRow)
 
       _grid[i] = row
     }