diff --git a/days/src/main/kotlin/Day24.kt b/days/src/main/kotlin/Day24.kt
index 54a43a3..e90aa48 100644
--- a/days/src/main/kotlin/Day24.kt
+++ b/days/src/main/kotlin/Day24.kt
@@ -4,6 +4,8 @@ import be.vandewalleh.aoc.utils.input.Day
 import be.vandewalleh.aoc.utils.input.Input
 import be.vandewalleh.aoc.utils.input.Lines
 import be.vandewalleh.aoc.utils.input.createDay
+import org.eclipse.collections.api.bag.Bag
+import org.eclipse.collections.api.bag.MutableBag
 import org.eclipse.collections.api.factory.Bags
 
 @Day(24)
@@ -20,29 +22,55 @@ class Day24(@Lines val input: Input<List<String>>) {
         val coordinates = coordinates
     }
 
-    private data class Tile(val directions: List<Direction>)
+    private fun parseTile(line: String) = "e|se|sw|w|nw|ne".toRegex()
+        .findAll(line)
+        .flatMap { it.groupValues }
+        .map { Direction.valueOf(it.toUpperCase()) }
+        .toList()
 
-    private fun parseTile(line: String): Tile {
-        val re = "e|se|sw|w|nw|ne".toRegex()
-        val directions = re.findAll(line).flatMap { it.groupValues }.map { Direction.valueOf(it.toUpperCase()) }
-        return Tile(directions.toList())
+    private val tiles = input.value.map { parseTile(it) }.map {
+        it.map { it.coordinates }
+            .reduce { acc, ints -> intArrayOf(acc[0] + ints[0], acc[1] + ints[1], acc[2] + ints[2]) }
+            .toList()
     }
 
-    fun part1() {
-        val tiles = input.value.map { parseTile(it) }
-        val bag = Bags.mutable.empty<List<Int>>()
-        for (tile in tiles) {
-            val encountered = tile.directions
-                .map { it.coordinates }
-                .reduce { acc, ints -> intArrayOf(acc[0] + ints[0], acc[1] + ints[1], acc[2] + ints[2]) }
-                .toList()
-            bag.add(encountered)
+    fun part1() = Bags.immutable.ofAll(tiles).selectBlacks().size()
+
+    private fun Bag<List<Int>>.selectBlacks() = selectByOccurrences { it % 2 == 1 }
+
+    private fun List<Int>.adjacents(): List<List<Int>> {
+        val (x, y, z) = this
+        return listOf(
+            listOf(x + 1, y - 1, z),
+            listOf(x, y - 1, z + 1),
+            listOf(x - 1, y, z + 1),
+            listOf(x - 1, y + 1, z),
+            listOf(x, y + 1, z - 1),
+            listOf(x + 1, y, z - 1),
+        )
+    }
+
+    // black -> odd
+    // white -> even || not in bag -> !in black
+    private fun day(bag: MutableBag<List<Int>>) {
+        val blacks = bag.selectBlacks().toSet()
+
+        val all = (bag + bag.flatMap { it.adjacents() }).toSet()
+
+        for (tile in all) {
+            val adjacents = tile.adjacents()
+            val adjacentBlacks = adjacents.count { it in blacks }
+            val isBlack = tile in blacks
+
+            if (isBlack && (adjacentBlacks == 0 || adjacentBlacks > 2)) bag.setOccurrences(tile, 2)
+            else if (!isBlack && adjacentBlacks == 2) bag.setOccurrences(tile, 1)
         }
-        println(bag.selectByOccurrences { it % 2 == 1 }.size)
     }
 
-    fun part2() {
-
+    fun part2(): Int {
+        val bag = Bags.mutable.ofAll(tiles)
+        repeat(100) { day(bag) }
+        return bag.selectBlacks().size()
     }
 }