diff --git a/source/app.d b/source/app.d
index 9466856..153ffa9 100644
--- a/source/app.d
+++ b/source/app.d
@@ -1,7 +1,7 @@
 import std.stdio;
 
-import day10.part1;
+import day11.part1;
 
 void main() {
-	syntaxChecker();
+	dumboOctopus();
 }
diff --git a/source/day11/input.txt b/source/day11/input.txt
new file mode 100644
index 0000000..df77777
--- /dev/null
+++ b/source/day11/input.txt
@@ -0,0 +1,10 @@
+4112256372
+3143253712
+4516848631
+3783477137
+3746723582
+5861358884
+4843351774
+2316447621
+6643817745
+6366815868
diff --git a/source/day11/part1.d b/source/day11/part1.d
new file mode 100644
index 0000000..589f039
--- /dev/null
+++ b/source/day11/part1.d
@@ -0,0 +1,110 @@
+module day11.part1;
+
+import std.file;
+import std.stdio;
+import std.string;
+import std.algorithm;
+import std.conv;
+import std.array;
+
+struct Point { size_t r; size_t c; }
+
+Point[] getAdjacentPoints(ubyte[][] map, Point p) {
+    size_t size = map.length;
+    Point[] points = [];
+    if (p.r > 0 && p.c > 0) points ~= Point(p.r - 1, p.c - 1);
+    if (p.r > 0) points ~= Point(p.r - 1, p.c);
+    if (p.c > 0) points ~= Point(p.r, p.c - 1);
+    if (p.r > 0 && p.c + 1 < size) points ~= Point(p.r - 1, p.c + 1);
+    if (p.c + 1 < size) points ~= Point(p.r, p.c + 1);
+    if (p.r + 1 < size) points ~= Point(p.r + 1, p.c);
+    if (p.r + 1 < size && p.c > 0) points ~= Point(p.r + 1, p.c - 1);
+    if (p.r + 1 < size && p.c + 1 < size) points ~= Point(p.r + 1, p.c + 1);
+    return points;
+}
+
+uint flash(ref ubyte[][] map, size_t row, size_t col, ref bool[][] flashed) {
+    Point[] neighbors = getAdjacentPoints(map, Point(row, col));
+    uint flashes = 1;
+    flashed[row][col] = true;
+    foreach (n; neighbors) {
+        if (!flashed[n.r][n.c]) {
+            map[n.r][n.c]++;
+            if (map[n.r][n.c] > 9) {
+                flashes += flash(map, n.r, n.c, flashed);
+            }
+        }
+    }
+    return flashes;
+}
+
+uint doStepPart1(ref ubyte[][] map) {
+    bool[][] flashed;
+    flashed.length = map.length;
+    foreach (r, row; map) {
+        flashed[r].length = map.length;
+        foreach (c, e; row) {
+            map[r][c]++;
+        }
+    }
+    uint flashes = 0;
+    foreach (r, row; map) {
+        foreach (c, e; row) {
+            if (e > 9 && !flashed[r][c]) {
+                flashes += flash(map, r, c, flashed);
+            }
+        }
+    }
+    bool allFlashed = true;
+    foreach (r, row; map) {
+        foreach (c, e; row) {
+            if (flashed[r][c]) {
+                map[r][c] = 0;
+            } else {
+                allFlashed = false;
+            }
+        }
+    }
+    return flashes;
+}
+
+uint doStepPart2(ref ubyte[][] map) {
+    bool[][] flashed;
+    flashed.length = map.length;
+    foreach (r, row; map) {
+        flashed[r].length = map.length;
+        foreach (c, e; row) {
+            map[r][c]++;
+        }
+    }
+    uint flashes = 0;
+    foreach (r, row; map) {
+        foreach (c, e; row) {
+            if (e > 9 && !flashed[r][c]) {
+                flashes += flash(map, r, c, flashed);
+            }
+        }
+    }
+    foreach (r, row; map) {
+        foreach (c, e; row) {
+            if (flashed[r][c]) {
+                map[r][c] = 0;
+            }
+        }
+    }
+    return flashes == (map.length * map.length);
+}
+
+void dumboOctopus() {
+    ubyte[][] map = readText("source/day11/input.txt").strip.split("\n")
+        .map!(s => s.strip.map!(c => cast(ubyte)(c.to!ubyte - '0')).array)
+        .array;
+    ulong i = 0;
+    while (true) {
+        if (doStepPart2(map)) {
+            writefln("All flashed at: %d", i + 1);
+            break;
+        }
+        i++;
+    }
+}
\ No newline at end of file
diff --git a/source/day11/test_input.txt b/source/day11/test_input.txt
new file mode 100644
index 0000000..03743f6
--- /dev/null
+++ b/source/day11/test_input.txt
@@ -0,0 +1,10 @@
+5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526