diff --git a/days/src/main/kotlin/Day20.kt b/days/src/main/kotlin/Day20.kt
index cd45d88..556b10d 100644
--- a/days/src/main/kotlin/Day20.kt
+++ b/days/src/main/kotlin/Day20.kt
@@ -7,6 +7,8 @@ import be.vandewalleh.aoc.utils.input.Day
 import be.vandewalleh.aoc.utils.input.Groups
 import be.vandewalleh.aoc.utils.input.Input
 import be.vandewalleh.aoc.utils.input.createDay
+import java.util.*
+import kotlin.collections.ArrayList
 import kotlin.math.sqrt
 
 private typealias Tile = Grid<Char>
@@ -121,126 +123,96 @@ class Day20(@Groups val input: Input<List<List<String>>>) {
         return grid
     }
 
+    private fun removeGaps(grid: Grid<Tile?>) {
+        for (y in 0 until grid.height) {
+            for (x in 0 until grid.width) {
+                grid[x, y] = removeGaps(grid[x, y]!!)
+            }
+        }
+    }
+
+    private fun removeGaps(tile: Tile): Tile {
+        val oldData: ArrayList<ArrayList<Char>> = tile.data
+        val newData = ArrayList<ArrayList<Char>>(oldData.size - 2)
+        oldData.subList(1, oldData.size - 1).forEach { d ->
+            val l = ArrayList<Char>().apply {
+                addAll(d.subList(1, d.size - 1))
+            }
+            newData.add(l)
+        }
+        return Tile(newData)
+    }
+
+    private fun gridToTile(grid: Grid<Tile?>): Tile {
+        val newData = ArrayList<ArrayList<Char>>()
+        for (y in 0 until grid.height) {
+            val row = grid.row(y)
+            for (yy in 0 until row[0]!!.height) {
+                val combinedRow = ArrayList<Char>()
+                row.forEach { combinedRow.addAll(it!!.row(yy)) }
+                newData.add(combinedRow)
+            }
+        }
+        return Tile(newData)
+    }
+
+    private fun Tile.subGridData(startX: Int, startY: Int, width: Int, height: Int): List<List<Char>> {
+        val newData = ArrayList<ArrayList<Char>>()
+        for (y in startY until startY + height) {
+            val row = ArrayList<Char>()
+            newData.add(row)
+            for (x in startX until startX + width) {
+                row.add(this[x, y]!!)
+            }
+        }
+        return newData
+    }
+
+    private fun List<List<Char>>.isMonster(monster: List<List<Char>>): Boolean {
+        val monsterRe = monster.joinToString("") { it.joinToString("") }.replace(" ", ".").toRegex()
+        val str = this.joinToString("") { it.joinToString("") }
+        return monsterRe.matches(str)
+    }
+
     fun part2() {
         val grid = assembleGrid()
-        TODO()
+        removeGaps(grid)
+        val megaTile = gridToTile(grid)
+
+        val monster: List<List<Char>> = """
+            |                  # |
+            |#    ##    ##    ###|
+            | #  #  #  #  #  #   |
+        """.trimMargin("|").lines().map { it.toCharArray().toList().dropLast(1) }
+
+        println(monster)
+
+        val monsterWidth = monster[0].size
+        val monsterHeight = 3
+        val monsterSquares = monster.joinToString("") { it.joinToString("") }.count { it == '#' }
+
+        val squares = megaTile.data.joinToString("") { it.joinToString("") }.count { it == '#' }
+
+        for (g: Tile in megaTile.transformations()) {
+            var count = 0
+            for (y in 0 until g.lastRowIndex - monsterHeight) {
+                for (x in 0 until g.lastColumnIndex - monsterWidth) {
+                    val subgrid = g.subGridData(x, y, monsterWidth, monsterHeight)
+                    if (subgrid.isMonster(monster)) {
+                        count++
+                    }
+                }
+            }
+            if (count != 0) {
+                println(count)
+                println(squares - (count * monsterSquares))
+            }
+        }
     }
 
 }
 
-fun main() {
-    with(createDay<Day20>(
-        """
-            Tile 2311:
-            ..##.#..#.
-            ##..#.....
-            #...##..#.
-            ####.#...#
-            ##.##.###.
-            ##...#.###
-            .#.#.#..##
-            ..#....#..
-            ###...#.#.
-            ..###..###
-
-            Tile 1951:
-            #.##...##.
-            #.####...#
-            .....#..##
-            #...######
-            .##.#....#
-            .###.#####
-            ###.##.##.
-            .###....#.
-            ..#.#..#.#
-            #...##.#..
-
-            Tile 1171:
-            ####...##.
-            #..##.#..#
-            ##.#..#.#.
-            .###.####.
-            ..###.####
-            .##....##.
-            .#...####.
-            #.##.####.
-            ####..#...
-            .....##...
-
-            Tile 1427:
-            ###.##.#..
-            .#..#.##..
-            .#.##.#..#
-            #.#.#.##.#
-            ....#...##
-            ...##..##.
-            ...#.#####
-            .#.####.#.
-            ..#..###.#
-            ..##.#..#.
-
-            Tile 1489:
-            ##.#.#....
-            ..##...#..
-            .##..##...
-            ..#...#...
-            #####...#.
-            #..#.#.#.#
-            ...#.#.#..
-            ##.#...##.
-            ..##.##.##
-            ###.##.#..
-
-            Tile 2473:
-            #....####.
-            #..#.##...
-            #.##..#...
-            ######.#.#
-            .#...#.#.#
-            .#########
-            .###.#..#.
-            ########.#
-            ##...##.#.
-            ..###.#.#.
-
-            Tile 2971:
-            ..#.#....#
-            #...###...
-            #.#.###...
-            ##.##..#..
-            .#####..##
-            .#..####.#
-            #..#.#..#.
-            ..####.###
-            ..#.#.###.
-            ...#.#.#.#
-
-            Tile 2729:
-            ...#.#.#.#
-            ####.#....
-            ..#.#.....
-            ....#..#.#
-            .##..##.#.
-            .#.####...
-            ####.#.#..
-            ##.####...
-            ##..#.##..
-            #.##...##.
-
-            Tile 3079:
-            #.#.#####.
-            .#..######
-            ..#.......
-            ######....
-            ####.#..#.
-            .#...#.##.
-            #.#####.##
-            ..#.###...
-            ..#.......
-            ..#.###...
-        """.trimIndent()
-    )) {
-        println(part1())
-        println(part2())
-    }
+fun main() = with(createDay<Day20>()) {
+    println(part1())
+    println(part2())
 }