diff --git a/2021/day19/input b/2021/day19/input
new file mode 100644
index 0000000..e2f977f
--- /dev/null
+++ b/2021/day19/input
@@ -0,0 +1,856 @@
+--- scanner 0 ---
+785,-772,752
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+
+--- scanner 1 ---
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+
+--- scanner 2 ---
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+
+--- scanner 3 ---
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+
+--- scanner 4 ---
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+
+--- scanner 5 ---
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+
+--- scanner 6 ---
+-665,672,665
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+
+--- scanner 7 ---
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+
+--- scanner 8 ---
+-834,731,729
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+
+--- scanner 9 ---
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+
+--- scanner 10 ---
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+
+--- scanner 11 ---
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+
+--- scanner 12 ---
+-438,505,-689
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+
+--- scanner 13 ---
+-830,923,434
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+
+--- scanner 14 ---
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+
+--- scanner 15 ---
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+
+--- scanner 16 ---
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+
+--- scanner 17 ---
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+
+--- scanner 18 ---
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+
+--- scanner 19 ---
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+
+--- scanner 20 ---
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+
+--- scanner 21 ---
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+
+--- scanner 22 ---
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+
+--- scanner 23 ---
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+
+--- scanner 24 ---
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+
+--- scanner 25 ---
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+
+--- scanner 26 ---
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+
+--- scanner 27 ---
+-781,-794,775
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+
+--- scanner 28 ---
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+-456,959,-777
+
+--- scanner 29 ---
+-741,-481,-792
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+394,271,253
+
+--- scanner 30 ---
+850,573,-382
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+420,-673,-815
diff --git a/2021/day19/main.go b/2021/day19/main.go
new file mode 100644
index 0000000..50e8d8d
--- /dev/null
+++ b/2021/day19/main.go
@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("vim-go")
+}
diff --git a/2021/day19/testinput b/2021/day19/testinput
new file mode 100644
index 0000000..4e496e9
--- /dev/null
+++ b/2021/day19/testinput
@@ -0,0 +1,136 @@
+--- scanner 0 ---
+404,-588,-901
+528,-643,409
+-838,591,734
+390,-675,-793
+-537,-823,-458
+-485,-357,347
+-345,-311,381
+-661,-816,-575
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+-689,845,-530
+423,-701,434
+7,-33,-71
+630,319,-379
+443,580,662
+-789,900,-551
+459,-707,401
+
+--- scanner 1 ---
+686,422,578
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+515,917,-361
+-336,658,858
+95,138,22
+-476,619,847
+-340,-569,-846
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+413,935,-424
+-391,539,-444
+586,-435,557
+-364,-763,-893
+807,-499,-711
+755,-354,-619
+553,889,-390
+
+--- scanner 2 ---
+649,640,665
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+-784,533,-524
+-644,584,-595
+-588,-843,648
+-30,6,44
+-674,560,763
+500,723,-460
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+646,-828,498
+640,759,510
+-630,509,768
+-681,-892,-333
+673,-379,-804
+-742,-814,-386
+577,-820,562
+
+--- scanner 3 ---
+-589,542,597
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+-500,565,-823
+-660,373,557
+-458,-679,-417
+-488,449,543
+-626,468,-788
+338,-750,-386
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+-938,-730,414
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+-104,29,83
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+-778,-728,485
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+-438,-605,-362
+-469,-447,-387
+509,732,623
+647,635,-688
+-868,-804,481
+614,-800,639
+595,780,-596
+
+--- scanner 4 ---
+727,592,562
+-293,-554,779
+441,611,-461
+-714,465,-776
+-743,427,-804
+-660,-479,-426
+832,-632,460
+927,-485,-438
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diff --git a/2021/day20/input b/2021/day20/input
new file mode 100644
index 0000000..2afe0ac
--- /dev/null
+++ b/2021/day20/input
@@ -0,0 +1,102 @@
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diff --git a/2021/day20/main.go b/2021/day20/main.go
new file mode 100644
index 0000000..4c50b80
--- /dev/null
+++ b/2021/day20/main.go
@@ -0,0 +1,55 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	enhancement, inputImage := inp[0], h.StringSliceToCoordByteMap(inp[2:])
+	fmt.Println("# Part 1")
+	run(inputImage, enhancement, 2)
+	fmt.Println()
+	fmt.Println("# Part 2")
+	run(inputImage, enhancement, 50)
+}
+
+func run(image h.CoordByteMap, enhancement string, iters int) {
+	bg := byte('.')
+	for i := 0; i < iters; i++ {
+		image = enhance(image, enhancement, bg)
+		if bg == '#' {
+			bg = enhancement[511]
+		} else {
+			bg = enhancement[0]
+		}
+	}
+	fmt.Println("Lit pixels:", image.Count('#'))
+}
+
+func enhance(image h.CoordByteMap, enhancement string, bg byte) h.CoordByteMap {
+	pxToInt := func(c h.Coordinate) int {
+		var num int
+		for bldY := c.Y - 1; bldY <= c.Y+1; bldY++ {
+			for bldX := c.X - 1; bldX <= c.X+1; bldX++ {
+				num = num << 1
+				v := image.Opt(h.Coordinate{X: bldX, Y: bldY}, bg)
+				if v == '#' {
+					num |= 1
+				}
+			}
+		}
+		return num
+	}
+	next := h.NewCoordByteMap()
+	for y := image.TLY - 1; y <= image.BRY+1; y++ {
+		for x := image.TLX - 1; x <= image.BRX+1; x++ {
+			c := h.Coordinate{X: x, Y: y}
+			nv := enhancement[pxToInt(c)]
+			next.Put(c, nv)
+		}
+	}
+	return next
+}
diff --git a/2021/day20/testinput b/2021/day20/testinput
new file mode 100644
index 0000000..8fa4bd4
--- /dev/null
+++ b/2021/day20/testinput
@@ -0,0 +1,7 @@
+..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
+
+#..#.
+#....
+##..#
+..#..
+..###
diff --git a/helpers/coordinateByteMap.go b/helpers/coordinateByteMap.go
index cc15c6f..59d73ce 100644
--- a/helpers/coordinateByteMap.go
+++ b/helpers/coordinateByteMap.go
@@ -1,22 +1,43 @@
 package aoc
 
+import "fmt"
+
 type CoordByteMap struct {
 	Field  map[Coordinate]byte
 	Height int
 	Width  int
+
+	// The Top-Left-most X/Y
+	TLX, TLY int
+	// The Bottom-Right-most X/Y
+	BRX, BRY int
+}
+
+func NewCoordByteMap() CoordByteMap {
+	return CoordByteMap{
+		Field: make(map[Coordinate]byte),
+	}
 }
 
 func StringSliceToCoordByteMap(input []string) CoordByteMap {
 	ret := CoordByteMap{
 		Field:  make(map[Coordinate]byte),
 		Height: len(input),
-		Width:  0,
 	}
 	for y := range input {
 		for x := range input[y] {
-			ret.Field[Coordinate{X: x, Y: y}] = input[y][x]
-			if x+1 > ret.Width {
-				ret.Width = x + 1
+			ret.Put(Coordinate{X: x, Y: y}, input[y][x])
+		}
+	}
+	return ret
+}
+
+func (m *CoordByteMap) Count(b byte) int {
+	var ret int
+	for y := m.TLY; y <= m.BRY; y++ {
+		for x := m.TLX; x <= m.BRX; x++ {
+			if m.Get(Coordinate{X: x, Y: y}) == b {
+				ret++
 			}
 		}
 	}
@@ -38,19 +59,79 @@ func (m *CoordByteMap) Opt(pos Coordinate, def byte) byte {
 }
 
 func (m *CoordByteMap) Put(pos Coordinate, val byte) {
+	if pos.X < m.TLX {
+		m.TLX = pos.X
+	}
+	if pos.Y < m.TLY {
+		m.TLY = pos.Y
+	}
+	if pos.X > m.BRX {
+		m.BRX = pos.X
+	}
+	if pos.Y > m.BRY {
+		m.BRY = pos.Y
+	}
 	m.Field[pos] = val
 	if pos.X+1 > m.Width {
-		m.Width = pos.X + 1
+		m.Width = m.BRX - m.TLX + 1
 	}
 	if pos.Y+1 > m.Height {
-		m.Height = pos.Y + 1
+		m.Height = m.BRY - m.TLY + 1
 	}
 }
 
+func (m *CoordByteMap) GrowNorth(size int, val byte) {
+	tlY := m.TLY - 1
+	for x := m.TLX; x <= m.BRX; x++ {
+		m.Put(Coordinate{X: x, Y: tlY}, val)
+	}
+}
+func (m *CoordByteMap) GrowEast(size int, val byte) {
+	brX := m.BRX + 1
+	for y := m.TLY; y <= m.BRY; y++ {
+		m.Put(Coordinate{X: brX, Y: y}, val)
+	}
+}
+func (m *CoordByteMap) GrowSouth(size int, val byte) {
+	tlY := m.BRY + 1
+	for x := m.TLX; x <= m.BRX; x++ {
+		m.Put(Coordinate{X: x, Y: tlY}, val)
+	}
+}
+func (m *CoordByteMap) GrowWest(size int, val byte) {
+	brX := m.TLX - 1
+	for y := m.TLY; y <= m.BRY; y++ {
+		m.Put(Coordinate{X: brX, Y: y}, val)
+	}
+}
+
+// This grows the map in all directions
+func (m *CoordByteMap) Grow(size int, val byte) {
+	m.GrowNorth(size, val)
+	m.GrowEast(size, val)
+	m.GrowSouth(size, val)
+	m.GrowWest(size, val)
+}
+
+// Runs the passed function on every point in the map
+// returning a new bytemap
+func (m CoordByteMap) Map(l func(c Coordinate, in byte) byte) CoordByteMap {
+	i := m
+	for y := m.TLY; y <= m.BRY; y++ {
+		for x := m.TLX; x <= m.BRX; x++ {
+			c := Coordinate{X: x, Y: y}
+			nV := l(c, m.Get(c))
+			fmt.Println("MAP: Putting", string(nV), "at", c)
+			i.Put(c, l(c, m.Get(c)))
+		}
+	}
+	return i
+}
+
 func (m CoordByteMap) String() string {
 	var ret string
-	for y := 0; y <= m.Height; y++ {
-		for x := 0; x <= m.Width; x++ {
+	for y := m.TLY; y <= m.BRY; y++ {
+		for x := m.TLX; x <= m.BRX; x++ {
 			ret = ret + string(m.Field[Coordinate{X: x, Y: y}])
 		}
 		ret = ret + "\n"