diff --git a/bot/mcbot.go b/bot/mcbot.go
index 654cc54..cf8e09c 100644
--- a/bot/mcbot.go
+++ b/bot/mcbot.go
@@ -6,6 +6,7 @@ package bot
 
 import (
 	"context"
+	"errors"
 	"net"
 	"strconv"
 
@@ -34,11 +35,14 @@ func (c *Client) JoinServerWithDialer(d *net.Dialer, addr string) (err error) {
 func parseAddress(r *net.Resolver, addr string) (string, error) {
 	const missingPort = "missing port in address"
 	var port uint16
+	var addrErr *net.AddrError
 	host, portStr, err := net.SplitHostPort(addr)
-	if addrErr, ok := err.(*net.AddrError); ok && addrErr.Err == missingPort {
-		host, port = addr, DefaultPort
-	} else if err != nil {
-		return "", err
+	if err != nil {
+		if errors.As(err, &addrErr) {
+			host, port = addr, DefaultPort
+		} else {
+			return "", err
+		}
 	} else {
 		if portInt, err := strconv.ParseUint(portStr, 10, 16); err != nil {
 			port = DefaultPort
diff --git a/examples/genmaps/colors.gob b/examples/genmaps/colors.gob
new file mode 100644
index 0000000..1ea2afd
Binary files /dev/null and b/examples/genmaps/colors.gob differ
diff --git a/examples/genmaps/genmaps.go b/examples/genmaps/genmaps.go
new file mode 100644
index 0000000..40a4a08
--- /dev/null
+++ b/examples/genmaps/genmaps.go
@@ -0,0 +1,130 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"github.com/Tnze/go-mc/data/block"
+	"github.com/Tnze/go-mc/save"
+	"github.com/Tnze/go-mc/save/region"
+	"image"
+	"image/color"
+	"image/draw"
+	"log"
+	"os"
+	"path/filepath"
+	"unsafe"
+)
+
+var colors []color.RGBA64
+
+var (
+	regionsFold = flag.String("region", filepath.Join(os.Getenv("AppData"), ".minecraft", "saves", "World", "region"), "region directory path")
+)
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+
+	de, err := os.ReadDir(*regionsFold)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var min, max [2]int
+	updateMinMax := func(pos [2]int) {
+		mkmax(&max[0], &pos[0])
+		mkmax(&max[1], &pos[1])
+		mkmin(&min[0], &pos[0])
+		mkmin(&min[1], &pos[1])
+	}
+
+	// Open mca files
+	var rs = make(map[[2]int]*region.Region, len(de))
+	for _, dir := range de {
+		name := dir.Name()
+		path := filepath.Join(*regionsFold, name)
+		var pos [2]int // {x, z}
+		if _, err := fmt.Sscanf(name, "r.%d.%d.mca", &pos[0], &pos[1]); err != nil {
+			log.Printf("Error parsing file name of %s: %v, ignoring", name, err)
+			continue
+		}
+		updateMinMax(pos)
+
+		r, err := region.Open(path)
+		if err != nil {
+			log.Printf("Error when opening %s: %v, ignoring", name, err)
+			continue
+		}
+		rs[pos] = r
+	}
+	// To close mca files
+	defer func() {
+		for pos, r := range rs {
+			if err := r.Close(); err != nil {
+				log.Printf("Close r.%d.%d.mca error: %v", pos[0], pos[1], err)
+			}
+		}
+	}()
+
+	for pos, r := range rs {
+		var column save.Column
+		img := image.NewRGBA(image.Rect(0, 0, 32*16, 32*16))
+		for x := 0; x < 32; x++ {
+			for z := 0; z < 32; z++ {
+				if !r.ExistSector(x, z) {
+					continue
+				}
+				data, err := r.ReadSector(x, z)
+				if err != nil {
+					log.Printf("Read sector (%d.%d) error: %v", x, z, err)
+				}
+				if err := column.Load(data); err != nil {
+					log.Printf("Decode column (%d.%d) error: %v", x, z, err)
+				}
+
+				draw.Draw(
+					img, image.Rect(x*16, z*16, x*16+16, z*16+16),
+					drawColumn(&column), image.Pt(0, 0),
+					draw.Over,
+				)
+			}
+		}
+		savePng(img, fmt.Sprintf("r.%d.%d.png", pos[0], pos[1]))
+		log.Print(pos, r)
+	}
+}
+
+func drawColumn(column *save.Column) (img *image.RGBA) {
+	img = image.NewRGBA(image.Rect(0, 0, 16, 16))
+
+	s := column.Level.Sections
+	for i := range s {
+		s := s[i]
+		// calculate bits per block
+		bpb := len(s.BlockStates) * 64 / (16 * 16 * 16)
+		// skip empty
+		if len(s.BlockStates) == 0 {
+			continue
+		}
+		// decode section
+		//n := int(math.Max(4, math.Ceil(math.Log2(float64(len(s.Palette))))))
+
+		// decode status
+		data := *(*[]uint64)(unsafe.Pointer(&s.BlockStates)) // convert []int64 into []uint64
+		bs := save.NewBitStorage(bpb, 4096, data)
+		for y := 0; y < 16; y++ {
+			layerImg := image.NewRGBA(image.Rect(0, 0, 16, 16))
+			for i := 16*16 - 1; i >= 0; i-- {
+				b := block.ByID[block.StateID[uint32(bs.Get(y*16*16+i))]]
+				c := colors[b.ID]
+				layerImg.Set(i/16, i%16, c)
+			}
+			draw.Draw(
+				img, image.Rect(0, 0, 16, 16),
+				layerImg, image.Pt(0, 0),
+				draw.Over,
+			)
+		}
+	}
+	return
+}
diff --git a/examples/genmaps/util_funcs.go b/examples/genmaps/util_funcs.go
new file mode 100644
index 0000000..a2299c1
--- /dev/null
+++ b/examples/genmaps/util_funcs.go
@@ -0,0 +1,53 @@
+package main
+
+import (
+	"bytes"
+	_ "embed"
+	"encoding/gob"
+	"fmt"
+	"image"
+	"image/png"
+	"log"
+	"os"
+)
+
+func savePng(img image.Image, name string) {
+	f, err := os.Create(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if err := png.Encode(f, img); err != nil {
+		f.Close()
+		log.Fatal(err)
+	}
+
+	if err := f.Close(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+//go:embed colors.gob
+var colorsBin []byte // gob([]color.RGBA64)
+
+func init() {
+	if err := gob.NewDecoder(bytes.NewReader(colorsBin)).Decode(&colors); err != nil {
+		panic(err)
+	}
+}
+
+func usage() {
+	_, _ = fmt.Fprintf(os.Stderr, "usage: %s [-region <region path>] \n", os.Args[0])
+	os.Exit(1)
+}
+
+func mkmax(c, n *int) {
+	if *c < *n {
+		*c = *n
+	}
+}
+func mkmin(c, n *int) {
+	if *c > *n {
+		*c = *n
+	}
+}
diff --git a/save/save.go b/save/save.go
deleted file mode 100644
index 16890c0..0000000
--- a/save/save.go
+++ /dev/null
@@ -1 +0,0 @@
-package save