diff --git a/day18/lagoon.go b/day18/lagoon.go
index 12046f3..d25062a 100644
--- a/day18/lagoon.go
+++ b/day18/lagoon.go
@@ -184,19 +184,19 @@ func calcHeightWidth(instructions []Instruction) (height, width int) {
 }
 
 type Coord struct {
-	X, Y int
+	Col, Row int
 }
 
 func (c Coord) applyDirection(d Direction) Coord {
 	switch d {
 	case Upward:
-		c.Y -= 1
+		c.Row -= 1
 	case Downward:
-		c.Y += 1
+		c.Row += 1
 	case Leftward:
-		c.X -= 1
+		c.Col -= 1
 	case Rightward:
-		c.X += 1
+		c.Col += 1
 	}
 
 	return c
@@ -209,46 +209,48 @@ type Cell struct {
 }
 type Field struct {
 	Height, Width int
-	Cells         [][]*Cell
+	// Cells         [][]*Cell
+	Cells map[Coord]*Cell
+	MinRow, MaxRow, MinCol, MaxCol int
+}
+func (f *Field)confirmCoord(c Coord) {
+	if c.Row - 3 < f.MinRow {
+		f.MinRow = c.Row - 3
+	}
+	if c.Row + 3 > f.MaxRow {
+		f.MaxRow = c.Row + 3
+	}
+	if c.Col - 3 < f.MinCol {
+		f.MinCol = c.Col - 3
+	}
+	if c.Col + 3 > f.MaxCol {
+		f.MaxCol = c.Col + 3
+	}
 }
 
 func CreateField(height, width int) Field {
-	rows := make([][]*Cell, height)
-	for i := 0; i < height; i++ {
-		row := make([]*Cell, width)
-		rows[i] = row
-		// for j := 0; j < width; j++ {
-		// 	row[j] = &Cell{}
-		// }
-	}
 	return Field{
 		Height: height, Width: width,
-		Cells: rows,
+		Cells: make(map[Coord]*Cell),
 	}
 }
 
-func (f *Field) coordToIndices(c Coord) (row, col int) {
-	row = c.Y + (f.Height / 2)
-	col = c.X + (f.Width / 2)
-	return
-}
-
 func (f *Field) digByInstructions(instructions []Instruction) (borderAmount int) {
-	runnerCoord := Coord{X: 0, Y: 0}
-	row, col := f.coordToIndices(runnerCoord)
-	f.Cells[row][col] = &Cell{
+	runnerCoord := Coord{Col: 0, Row: 0}
+	f.Cells[runnerCoord] = &Cell{
 		IsDug: true,
 	}
+	f.confirmCoord(runnerCoord)
 	// borderAmount += 1
 
 	for _, instruction := range instructions {
 		log.Printf("starting instruction %+v", instruction)
 		for i := 0; i < instruction.Steps; i++ {
 			runnerCoord = runnerCoord.applyDirection(instruction.Direction)
-			row, col := f.coordToIndices(runnerCoord)
-			f.Cells[row][col] = &Cell{
+			f.Cells[runnerCoord] = &Cell{
 				IsDug: true,
 			}
+			f.confirmCoord(runnerCoord)
 			borderAmount += 1
 		}
 	}
@@ -257,56 +259,19 @@ func (f *Field) digByInstructions(instructions []Instruction) (borderAmount int)
 
 func (f *Field) String() string {
 	s := "text 15,15 \""
-	firstNonemptyRow, lastNonemptyRow := 0, 0
-	log.Print("just use", firstNonemptyRow, lastNonemptyRow)
-	seenInRows := false
-	firstNonemptyCol, lastNonemptyCol := 0, 0
-	seenInCols := false
 
-	for i, row := range f.Cells {
-		seenInRow := false
-		for j := 0; j < len(row); j++ {
-			if f.isCellDug(i, j) {
-				seenInRow = true
-			}
-		}
-		seenInRows = seenInRows || seenInRow
-		if seenInRow {
-			lastNonemptyRow = i
-		}
-		if !seenInRows {
-			firstNonemptyRow = i
-		}
-	}
-
-	for col := 0; col < f.Width; col++ {
-		seenInCol := false
-		for row := 0; row < f.Height; row++ {
-			if f.isCellDug(row, col) {
-				seenInCol = true
-			}
-		}
-		seenInCols = seenInCols || seenInCol
-		if seenInCol {
-			lastNonemptyCol = col
-		}
-		if !seenInCols {
-			firstNonemptyCol = col
-		}
-	}
-
-	rowLen := lastNonemptyCol - firstNonemptyCol + 1
-	log.Print(rowLen)
-	for i := 0; i <= f.Height-1; i++ {
-		rowChars := make([]rune, f.Width)
-		for col := 0; col <= f.Width-1; col++ {
-			cell := f.Cells[i][col]
+	for row := f.MinRow; row <= f.MaxRow; row++ {
+		rowChars := make([]rune, f.MaxCol - f.MinCol + 1)
+		for col := f.MinCol; col <= f.MaxCol; col++ {
+			cell := f.Cells[Coord{col, row}]
 			if cell != nil && cell.ToBeDug {
-				rowChars[col] = '@'
-			} else if f.isCellDug(i, col) {
-				rowChars[col] = '#'
+				rowChars[col - f.MinCol] = '@'
+				continue
+			}
+			if f.isCellDug(row, col) {
+				rowChars[col - f.MinCol] = '#'
 			} else {
-				rowChars[col] = '.'
+				rowChars[col - f.MinCol] = '.'
 			}
 		}
 
@@ -318,10 +283,10 @@ func (f *Field) String() string {
 }
 
 func (f *Field) digInsides() (countInside int) {
-	for row := 1; row < f.Height-1; row++ {
+	for row := f.MinRow; row < f.MaxRow; row++ {
 		isInside := false
 		seenUp, seenDown := false, false // for detecting L---7 walls
-		for col := 0; col < f.Width-1; col++ {
+		for col := f.MinCol; col < f.MaxCol; col++ {
 			rightCellIsDug := f.isCellDug(row, col+1)
 			if f.isCellDug(row, col) {
 				upCellIsDug := f.isCellDug(row-1, col)
@@ -335,9 +300,9 @@ func (f *Field) digInsides() (countInside int) {
 			} else {
 				// not a dug out cell, maybe inside and needs to be dug out
 				if isInside {
-					f.Cells[row][col] = &Cell{
-						ToBeDug: true,
-					}
+					// f.Cells[Coord{col, row}] = &Cell{
+					// 	ToBeDug: true,
+					// }
 
 					countInside += 1
 					log.Printf("tick count inside for %d %d", row, col)
@@ -355,21 +320,10 @@ func (f *Field) digInsides() (countInside int) {
 }
 
 func (f *Field) isCellDug(row, col int) bool {
-	cell := f.Cells[row][col]
+	cell := f.Cells[Coord{col, row}]
 	return cell != nil && cell.IsDug
 }
 
-// func (f *Field)countDugOut() (result int) {
-// 	for _, row := range f.Cells {
-// 		for _, cell := range row {
-// 			if cell.IsDug || cell.ToBeDug {
-// 				result += 1
-// 			}
-// 		}
-// 	}
-// 	return
-// }
-
 func WriteToFile(filename string, content string) {
 	fileBorder, err := os.Create(filename)
 	if err != nil {