diff --git a/2020/day16/main.go b/2020/day16/main.go
index 7e89e9f..028e046 100644
--- a/2020/day16/main.go
+++ b/2020/day16/main.go
@@ -14,7 +14,7 @@ var FieldMap map[int]string
 var UnknownFields map[int]bool
 
 func main() {
-	fmt.Println("# Day 15")
+	fmt.Println("# Day 16")
 	inp := h.StdinToStringSlice()
 	FieldMap = make(map[int]string)
 	UnknownFields = make(map[int]bool)
diff --git a/2020/day17/input b/2020/day17/input
new file mode 100644
index 0000000..9511cae
--- /dev/null
+++ b/2020/day17/input
@@ -0,0 +1,8 @@
+....###.
+#...####
+##.#.###
+..#.#...
+##.#.#.#
+#.######
+..#..#.#
+######.#
diff --git a/2020/day17/main.go b/2020/day17/main.go
new file mode 100644
index 0000000..7ff3d89
--- /dev/null
+++ b/2020/day17/main.go
@@ -0,0 +1,115 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	fmt.Println("# Day 17")
+	fmt.Println()
+	inp := h.StdinToStringSlice()
+	//field := h.StringSliceToCoord3dByteMap(inp)
+	//part1old(field)
+	fmt.Println("## Part 1:\nAnswer:", run(inp, 3))
+	fmt.Println("## Part 2:\nAnswer:", run(inp, 4))
+}
+
+func run(inp []string, dim int) int {
+	cs := NewCubeMapFromLines(inp)
+	for i := 0; i < 6; i++ {
+		next := NewCubeMap()
+		wrk := cs.Copy()
+		for _, c := range cs.ToSlice() {
+			wrk.AddMany(c.Neighbors(dim))
+		}
+		for _, c := range wrk.ToSlice() {
+			active := cs.Contains(c)
+			cnt := 0
+			for _, n := range c.Neighbors(dim) {
+				if cs.Contains(n) {
+					cnt++
+				}
+			}
+			if cnt == 3 || (active && cnt == 2) {
+				next.Add(c)
+			}
+		}
+		cs = next
+	}
+	return cs.Size()
+}
+
+type Cube struct {
+	X, Y, Z, W int
+}
+
+func (c Cube) Neighbors(d int) []Cube {
+	ret := []Cube{}
+	for dx := -1; dx <= 1; dx++ {
+		for dy := -1; dy <= 1; dy++ {
+			for dz := -1; dz <= 1; dz++ {
+				for dw := -(d - 3); dw <= d-3; dw++ {
+					if dx == 0 && dy == 0 && dz == 0 && dw == 0 {
+						continue
+					}
+					ret = append(ret, Cube{c.X + dx, c.Y + dy, c.Z + dz, c.W + dw})
+				}
+			}
+		}
+	}
+	return ret
+}
+
+type CubeMap struct {
+	field map[Cube]bool
+}
+
+func NewCubeMap() *CubeMap {
+	return &CubeMap{map[Cube]bool{}}
+}
+func NewCubeMapFromLines(inp []string) *CubeMap {
+	cs := NewCubeMap()
+	for y, line := range inp {
+		for x, b := range line {
+			if b == '#' {
+				cs.Add(Cube{x, y, 0, 0})
+			}
+		}
+	}
+	return cs
+}
+
+func (cs *CubeMap) Add(c Cube) {
+	cs.field[c] = true
+}
+func (cs *CubeMap) AddMany(cubes []Cube) {
+	for _, c := range cubes {
+		cs.Add(c)
+	}
+}
+func (cs *CubeMap) Remove(c Cube) {
+	delete(cs.field, c)
+}
+func (cs *CubeMap) Contains(c Cube) bool {
+	_, ok := cs.field[c]
+	return ok
+}
+func (cs *CubeMap) Copy() *CubeMap {
+	field := map[Cube]bool{}
+	for c := range cs.field {
+		field[c] = true
+	}
+	return &CubeMap{field}
+}
+func (cs *CubeMap) Size() int {
+	return len(cs.field)
+}
+func (cs *CubeMap) ToSlice() []Cube {
+	ret := []Cube{}
+	for c := range cs.field {
+		ret = append(ret, Cube{c.X, c.Y, c.Z, c.W})
+	}
+	return ret
+}
diff --git a/2020/day17/testinput b/2020/day17/testinput
new file mode 100644
index 0000000..eedd3d2
--- /dev/null
+++ b/2020/day17/testinput
@@ -0,0 +1,3 @@
+.#.
+..#
+###
diff --git a/helpers/coordinate3d.go b/helpers/coordinate3d.go
index 665bf8b..7cd50ce 100644
--- a/helpers/coordinate3d.go
+++ b/helpers/coordinate3d.go
@@ -72,5 +72,5 @@ func (c *Coordinate3d) GetDownCoord() *Coordinate3d {
 	}
 }
 func (c Coordinate3d) String() string {
-	return fmt.Sprintf("[%d, %d, %d]", c.X, c.Y, c.Z)
+	return fmt.Sprintf("[X:%d, Y:%d, Z:%d]", c.X, c.Y, c.Z)
 }
diff --git a/helpers/coordinateByteMap.go b/helpers/coordinateByteMap.go
index 8ce0bb0..28e53a4 100644
--- a/helpers/coordinateByteMap.go
+++ b/helpers/coordinateByteMap.go
@@ -24,12 +24,19 @@ func StringSliceToCoordByteMap(input []string) CoordByteMap {
 }
 
 func (m *CoordByteMap) Get(pos Coordinate) byte {
-	if pos.X <= m.Width && pos.Y <= m.Height {
-		return m.Field[pos]
+	if v, ok := m.Field[pos]; ok {
+		return v
 	}
 	return 0
 }
 
+func (m *CoordByteMap) Opt(pos Coordinate, def byte) byte {
+	if v, ok := m.Field[pos]; ok {
+		return v
+	}
+	return def
+}
+
 func (m *CoordByteMap) Put(pos Coordinate, val byte) {
 	m.Field[pos] = val
 }
@@ -44,3 +51,118 @@ func (m CoordByteMap) String() string {
 	}
 	return ret
 }
+
+// And the 3d Version
+type Coord3dByteMap struct {
+	Field      map[Coordinate3d]byte
+	MinX, MaxX int
+	MinY, MaxY int
+	MinZ, MaxZ int
+}
+
+func StringSliceToCoord3dByteMap(input []string) Coord3dByteMap {
+	ret := Coord3dByteMap{
+		Field: make(map[Coordinate3d]byte),
+	}
+	for y := range input {
+		for x := range input[y] {
+			ret.Put(Coordinate3d{X: x, Y: y, Z: 0}, input[y][x])
+		}
+	}
+	return ret
+}
+
+func (m *Coord3dByteMap) Copy() Coord3dByteMap {
+	ret := Coord3dByteMap{
+		Field: make(map[Coordinate3d]byte),
+		MinX:  m.MinX, MaxX: m.MaxX,
+		MinY: m.MinY, MaxY: m.MaxY,
+		MinZ: m.MinZ, MaxZ: m.MaxZ,
+	}
+	for z := m.MinZ; z <= m.MaxZ; z++ {
+		for y := m.MinY; y <= m.MaxY; y++ {
+			for x := m.MinX; x <= m.MaxX; x++ {
+				c := Coordinate3d{X: x, Y: y, Z: z}
+				ret.Field[c] = m.Get(c)
+			}
+		}
+	}
+	return ret
+}
+
+func (m *Coord3dByteMap) Get(pos Coordinate3d) byte {
+	if _, ok := m.Field[pos]; !ok {
+		return 0
+	}
+	return m.Field[pos]
+}
+func (m *Coord3dByteMap) Opt(pos Coordinate3d, def byte) byte {
+	if v, ok := m.Field[pos]; ok {
+		return v
+	}
+	return def
+}
+
+func (m *Coord3dByteMap) Put(pos Coordinate3d, val byte) {
+	m.Field[pos] = val
+	if pos.X < m.MinX {
+		m.MinX = pos.X
+	}
+	if pos.X > m.MaxX {
+		m.MaxX = pos.X
+	}
+	if pos.Y < m.MinY {
+		m.MinY = pos.X
+	}
+	if pos.Y > m.MaxY {
+		m.MaxY = pos.Y
+	}
+	if pos.Z < m.MinZ {
+		m.MinZ = pos.Z
+	}
+	if pos.Z > m.MaxZ {
+		m.MaxZ = pos.Z
+	}
+}
+
+func (m *Coord3dByteMap) CountNeighbors(pos Coordinate3d, val byte) int {
+	var res int
+	for z := pos.Z - 1; z <= pos.Z+1; z++ {
+		for y := pos.Y - 1; y <= pos.Y+1; y++ {
+			for x := pos.X - 1; x <= pos.X+1; x++ {
+				if m.Get(Coordinate3d{X: x, Y: y, Z: z}) == val {
+					res++
+				}
+			}
+		}
+	}
+	return res
+}
+
+func (m Coord3dByteMap) Count(val byte) int {
+	var ret int
+	for z := m.MinZ; z <= m.MaxZ; z++ {
+		for y := m.MinY; y <= m.MaxY; y++ {
+			for x := m.MinX; x <= m.MaxX; x++ {
+				if m.Get(Coordinate3d{X: x, Y: y, Z: z}) == val {
+					ret++
+				}
+			}
+		}
+	}
+	return ret
+}
+
+func (m Coord3dByteMap) String() string {
+	var ret string
+	for z := m.MinZ; z <= m.MaxZ; z++ {
+		for y := m.MinY; y <= m.MaxY; y++ {
+			for x := m.MinX; x <= m.MaxX; x++ {
+				ret = ret + string(m.Field[Coordinate3d{X: x, Y: y, Z: z}])
+			}
+			ret = ret + "\n"
+		}
+		ret = ret + "\n\n"
+	}
+	return ret
+}