diff --git a/data/biomes.go b/data/biomes.go
index 2cae67a..64af1c1 100644
--- a/data/biomes.go
+++ b/data/biomes.go
@@ -1,5 +1,7 @@
 package data
 
+import "errors"
+
 // [
 //
 //	{
@@ -48,6 +50,8 @@ func LookupBiomeById(version string, id int32) (biome *Biome, ok bool) {
 	return
 }
 
+var UnknownBiomeNameErr = errors.New("unknown biome Name")
+
 func LookupBiomeByName(version string, name string) (biome *Biome, ok bool) {
 	for _, b := range BiomesForVersion(version) {
 		if b.Name == name {
diff --git a/data/blocks.go b/data/blocks.go
index b211c9e..f3bae8a 100644
--- a/data/blocks.go
+++ b/data/blocks.go
@@ -81,6 +81,8 @@ func LookupBlockByStateId(version string, stateId int32) (block *Block, ok bool)
 	return
 }
 
+var UnknownBlockNameErr = errors.New("unknown block Name")
+
 func LookupBlockByName(version string, name string) (block *Block, ok bool) {
 	for _, b := range BlocksForVersion(version) {
 		if b.Name == name {
diff --git a/level/chunk_builder.go b/level/chunk_builder.go
new file mode 100644
index 0000000..1903f9e
--- /dev/null
+++ b/level/chunk_builder.go
@@ -0,0 +1,93 @@
+package level
+
+import (
+	"bytes"
+	"errors"
+
+	"github.com/admin-else/strom/data"
+	"github.com/admin-else/strom/util"
+)
+
+type ChunkBuilder struct {
+	Biomes, Blocks [][]int32
+	Bottom, Top    int32
+	Version        string
+}
+
+func NewChunkBuilder(bottom, top int32, version string) *ChunkBuilder {
+	return &ChunkBuilder{Bottom: bottom, Top: top, Version: version}
+}
+
+func NewOverworldChunkBuilder(version string) *ChunkBuilder {
+	return NewChunkBuilder(-64, 320, version)
+}
+
+func (cb *ChunkBuilder) ColumnHeight() int32 {
+	absBottom := cb.Bottom
+	if absBottom < 0 {
+		absBottom *= -1
+	}
+	return absBottom + cb.Top
+}
+
+func (cb *ChunkBuilder) FillAllById(block, biome int32) {
+	numSections := cb.ColumnHeight() / ChunkWidth
+	blockSection := util.MakeSingleValuedSlice(block, BlocksPerChunkSection)
+	biomeSection := util.MakeSingleValuedSlice(biome, BiomesPerChunkSection)
+	cb.Blocks = make([][]int32, numSections)
+	cb.Biomes = make([][]int32, numSections)
+	for i := range cb.Blocks {
+		cb.Blocks[i] = blockSection
+		cb.Biomes[i] = biomeSection
+	}
+	return
+}
+
+func (cb *ChunkBuilder) FillAll(biome, block string) (err error) {
+	blockData, ok := data.LookupBlockByName(cb.Version, block)
+	if !ok {
+		err = data.UnknownBlockNameErr
+		return
+	}
+	biomeData, ok := data.LookupBiomeByName(cb.Version, biome)
+	if !ok {
+		err = data.UnknownBiomeNameErr
+		return
+	}
+	cb.FillAllById(blockData.DefaultState, biomeData.Id)
+	return
+}
+
+var InvalidChunkPositionErr = errors.New("invalid chunk position")
+
+func (cb *ChunkBuilder) SetBlockId(x, y, z, id int32) (err error) {
+	if x < 0 || x >= ChunkWidth || z < 0 || z >= ChunkWidth || y < cb.Bottom || y >= cb.Top {
+		err = InvalidChunkPositionErr
+		return
+	}
+
+	y += cb.Bottom * -1
+	section := util.FloorDiv(y, ChunkWidth)
+	i := (y%ChunkWidth)*ChunkWidth*ChunkWidth + z*ChunkWidth + x
+	cb.Blocks[section][i] = id
+	return
+}
+
+func (cb *ChunkBuilder) SetBlock(x, y, z int32, block string) (err error) {
+	blockData, ok := data.LookupBlockByName(cb.Version, block)
+	if !ok {
+		err = data.UnknownBlockNameErr
+		return
+	}
+	return cb.SetBlockId(x, y, z, blockData.DefaultState)
+}
+
+func (cb *ChunkBuilder) Build() (data []byte, err error) {
+	b := bytes.NewBuffer(nil)
+	err = PackSections(cb.Blocks, cb.Biomes, cb.Version, b)
+	if err != nil {
+		return
+	}
+	data = b.Bytes()
+	return
+}
diff --git a/level/packet.go b/level/packet.go
index 4d3a597..1df53f2 100644
--- a/level/packet.go
+++ b/level/packet.go
@@ -12,7 +12,8 @@ import (
 )
 
 const (
-	BlocksPerChunkSection = 16 * 16 * 16
+	ChunkWidth            = 16
+	BlocksPerChunkSection = ChunkWidth * ChunkWidth * ChunkWidth
 	BiomesPerChunkSection = 4 * 4 * 4
 )
 
diff --git a/util/math.go b/util/math.go
new file mode 100644
index 0000000..3c8e383
--- /dev/null
+++ b/util/math.go
@@ -0,0 +1,5 @@
+package util
+
+func FloorDiv(a, b int32) int32 {
+	return (a - ((a%b + b) % b)) / b
+}
diff --git a/util/must.go b/util/must.go
index 12e2053..6ecbe3b 100644
--- a/util/must.go
+++ b/util/must.go
@@ -6,3 +6,16 @@ func MustOk[T any](v T, ok bool) T {
 	}
 	return v
 }
+
+func MustT[T any](v T, err error) T {
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func Must(err error) {
+	if err != nil {
+		panic(err)
+	}
+}