diff --git a/Day19.cs b/Day19.cs
index 80fdda2..0b03cdb 100644
--- a/Day19.cs
+++ b/Day19.cs
@@ -1,4 +1,4 @@
-#define Day19
+// #define Day19
 #if Day19
 using System.Collections.Immutable;
 using AoC2021;
diff --git a/Day20.cs b/Day20.cs
new file mode 100644
index 0000000..b5784cb
--- /dev/null
+++ b/Day20.cs
@@ -0,0 +1,83 @@
+#define Day20
+#if Day20
+using AoC2021;
+
+var lines = File.ReadAllLines("day20/input");
+var translate = lines[0].Select(c => c == '#' ? "1" : "0").ToList();
+
+int steps = 50;
+int size = lines.Length - 2;
+string[,] image = new string[size + 4,size + 4];
+
+lines.Skip(2).ForEachIndex((l, row) => 
+    l.ForEachIndex((c, col) => image[row + 2, col + 2] = c == '#' ? "1" : "0"));
+
+string infinite = "0";
+SetBorder(image, infinite);
+// Print(image);
+
+while (steps > 0) {
+    size = image.GetLength(0);
+    string[,] nextImage = new string[size + 2,size + 2];
+    for (int row = 1; row < size-1; row++) {
+        for (int col = 1; col < size-1; col++) {
+            nextImage[row + 1, col + 1] = GetNewPoint(row, col, image);
+        }
+    }
+
+    infinite = NextInfinite(infinite);
+    SetBorder(nextImage, infinite);
+
+    image = nextImage;
+    // Print(image);
+    // Console.WriteLine();
+    steps--;
+}
+
+int count = 0;
+for (int row = 0; row < image.GetLength(0); row++) {
+    for (int col = 0; col < image.GetLength(1); col++) {
+        if (image[row, col] == "1") {
+            count++;
+        }
+    }
+}
+
+Console.WriteLine(count);
+
+void Print(string[,] image) {
+    for (int row = 0; row < image.GetLength(0); row++) {
+        for (int col = 0; col < image.GetLength(1); col++) {
+            Console.Write(image[row, col] == "1" ? '#' : '.');
+        }
+
+        Console.WriteLine();
+    }
+}
+
+string GetNewPoint(int row, int col, string[,] imageToRead) {
+    var binary = imageToRead[row - 1, col - 1] + imageToRead[row - 1, col] + imageToRead[row - 1, col + 1]
+                 + imageToRead[row, col - 1] + imageToRead[row, col] + imageToRead[row, col + 1]
+                 + imageToRead[row + 1, col - 1] + imageToRead[row + 1, col] + imageToRead[row + 1, col + 1];
+    return translate[Convert.ToInt32(binary, 2)];
+}
+
+string NextInfinite(string infinite) {
+    var infinitePos = Convert.ToInt32(String.Join("",Enumerable.Repeat(infinite, 9)), 2);
+    return translate[infinitePos];
+}
+
+void SetBorder(string[,] image, string value) {
+    int last = image.GetLength(0) - 1;
+    Enumerable.Range(0, image.GetLength(0)).ForEachAsList(i => {
+        image[0, i] = value;
+        image[1, i] = value;
+        image[i, 0] = value;
+        image[i, 1] = value;
+        image[last, i] = value;
+        image[last-1, i] = value;
+        image[i, last] = value;
+        image[i, last-1] = value;
+    });
+}
+#endif
diff --git a/day20/input b/day20/input
new file mode 100644
index 0000000..3b5bb79
--- /dev/null
+++ b/day20/input
@@ -0,0 +1,102 @@
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+
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