diff --git a/day18/day.go b/day18/day.go
new file mode 100644
index 0000000..c024ba5
--- /dev/null
+++ b/day18/day.go
@@ -0,0 +1,75 @@
+package day18
+
+import (
+	"tools"
+)
+
+type coord struct {
+	x int
+	y int
+}
+
+func play(grid tools.ToggleGrid, stuckCorners bool) {
+	neighbours := make(map[coord]int)
+	for thisCoord := range grid.GetOnCoordinates() {
+		for cx := thisCoord.X - 1; cx <= thisCoord.X+1; cx++ {
+			for cy := thisCoord.Y - 1; cy <= thisCoord.Y+1; cy++ {
+				if cy == thisCoord.Y && cx == thisCoord.X {
+					continue
+				}
+				neighbours[coord{cx, cy}]++
+			}
+		}
+	}
+
+	for x := 0; x <= grid.MaxX; x++ {
+		for y := 0; y <= grid.MaxY; y++ {
+			if grid.State(x, y) {
+				if neighbours[coord{x, y}] != 2 && neighbours[coord{x, y}] != 3 {
+					if !stuckCorners || !grid.IsCorner(x, y) {
+						grid.Set(x, y, tools.Off)
+					}
+				}
+			} else if neighbours[coord{x, y}] == 3 {
+				grid.Set(x, y, tools.On)
+			}
+		}
+	}
+}
+
+func makeGridFromInput(input []string) tools.ToggleGrid {
+	grid := tools.NewToogleGrid()
+	for y, line := range input {
+		for x, c := range line {
+			if c == '#' {
+				grid.Set(x, y, tools.On)
+			}
+		}
+	}
+
+	return grid
+}
+
+func Part1(puzzle tools.AoCPuzzle) interface{} {
+	grid := makeGridFromInput(puzzle.GetInputArray())
+
+	for i := 0; i < 100; i++ {
+		play(grid, false)
+	}
+
+	return grid.GetOnCount()
+}
+
+func Part2(puzzle tools.AoCPuzzle) interface{} {
+	grid := makeGridFromInput(puzzle.GetInputArray())
+	grid.Set(0, 0, tools.On)
+	grid.Set(0, grid.MaxY, tools.On)
+	grid.Set(grid.MaxX, 0, tools.On)
+	grid.Set(grid.MaxX, grid.MaxY, tools.On)
+
+	for i := 0; i < 100; i++ {
+		play(grid, true)
+	}
+
+	return grid.GetOnCount()
+}
diff --git a/inputs/18 b/inputs/18
new file mode 100644
index 0000000..6a14c51
--- /dev/null
+++ b/inputs/18
@@ -0,0 +1,100 @@
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\ No newline at end of file
diff --git a/inputs/18_test b/inputs/18_test
new file mode 100644
index 0000000..51dc5ce
--- /dev/null
+++ b/inputs/18_test
@@ -0,0 +1,6 @@
+.#.#.#
+...##.
+#....#
+..#...
+#.#..#
+####..
\ No newline at end of file
diff --git a/main.go b/main.go
index 61fe5aa..e1a04f8 100644
--- a/main.go
+++ b/main.go
@@ -18,6 +18,7 @@ import (
 	"aoc2015/day15"
 	"aoc2015/day16"
 	"aoc2015/day17"
+	"aoc2015/day18"
 	"flag"
 	"fmt"
 	"os"
@@ -52,6 +53,7 @@ func initDayFunctions() {
 		15: {1: day15.Part1, 2: day15.Part2},
 		16: {1: day16.Part1, 2: day16.Part2},
 		17: {1: day17.Part1, 2: day17.Part2},
+		18: {1: day18.Part1, 2: day18.Part2},
 	}
 }