diff --git a/internal/editor/command.go b/internal/editor/command.go
index 0b2ce82..74dd862 100644
--- a/internal/editor/command.go
+++ b/internal/editor/command.go
@@ -5,7 +5,7 @@ func (ed *Editor) Insert() {
 	if ed.mode == ModeInsert {
 		panic("invalid state")
 	}
-	ed.ins.Enter(ed.lines[ed.row], ed.col)
+	ed.ins.Init(ed.CurrentLine(), ed.col)
 	ed.mode = ModeInsert
 }
 
@@ -28,7 +28,8 @@ func (ed *Editor) MoveLeft(n int) {
 	if ed.mode != ModeCommand {
 		panic("invalid state")
 	}
-	ed.col = max(ed.col-n, 0)
+	ed.col -= n
+	ed.Confine()
 }
 
 // key: l
@@ -36,7 +37,8 @@ func (ed *Editor) MoveRight(n int) {
 	if ed.mode != ModeCommand {
 		panic("invalid state")
 	}
-	ed.col = min(ed.col+n, max(ed.RuneCount()-1, 0))
+	ed.col += n
+	ed.Confine()
 }
 
 // key: j
@@ -44,7 +46,8 @@ func (ed *Editor) MoveDown(n int) {
 	if ed.mode != ModeCommand {
 		panic("invalid state")
 	}
-	ed.row = min(ed.row+n, max(len(ed.lines)-1, 0))
+	ed.row += n
+	ed.Confine()
 }
 
 // key: k
@@ -52,7 +55,8 @@ func (ed *Editor) MoveUp(n int) {
 	if ed.mode != ModeCommand {
 		panic("invalid state")
 	}
-	ed.row = max(ed.row-n, 0)
+	ed.row -= n
+	ed.Confine()
 }
 
 // key: x
@@ -60,11 +64,11 @@ func (ed *Editor) DeleteRune(n int) {
 	if ed.mode != ModeCommand {
 		panic("invalid state")
 	}
-	if len(ed.lines[ed.row]) < 1 {
+	if len(ed.CurrentLine()) < 1 {
 		ed.Ring()
 		return
 	}
-	rs := []rune(ed.lines[ed.row])
+	rs := []rune(ed.CurrentLine())
 	if ed.col < 1 {
 		ed.lines[ed.row] = string(rs[1:])
 	} else {
@@ -72,8 +76,5 @@ func (ed *Editor) DeleteRune(n int) {
 		tail := string(rs[ed.col+1:])
 		ed.lines[ed.row] = head + tail
 	}
-	rc := ed.RuneCount()
-	if ed.col >= rc {
-		ed.col = max(rc-1, 0)
-	}
+	ed.Confine()
 }
diff --git a/internal/editor/editor.go b/internal/editor/editor.go
index 4d0a4aa..33794df 100644
--- a/internal/editor/editor.go
+++ b/internal/editor/editor.go
@@ -17,8 +17,9 @@ const (
 
 type Editor struct {
 	col, row int
-	x, y     int
 	vrow     int
+	w, h     int
+	x, y     int
 	lines    []string
 	ins      *Insert
 	mode     Mode
@@ -26,15 +27,8 @@ type Editor struct {
 	bell     bool
 }
 
-func (ed *Editor) Load() {
-	if ed.path == "" {
-		return
-	}
-	_, err := os.Stat(ed.path)
-	if err != nil { // file not exists
-		return
-	}
-	data, err := os.ReadFile(ed.path)
+func (ed *Editor) Load(path string) {
+	data, err := os.ReadFile(path)
 	if err != nil {
 		panic(err)
 	}
@@ -46,6 +40,7 @@ func (ed *Editor) Load() {
 		data = data[:len(data)-1]
 	}
 	ed.lines = strings.Split(string(data), "\n")
+	ed.path = path
 }
 
 func Init(args []string) *Editor {
@@ -54,12 +49,15 @@ func Init(args []string) *Editor {
 		path = args[1]
 	}
 
+	w, h := termi.Size()
 	ed := &Editor{
 		col:   0,
 		row:   0,
+		vrow:  0,
+		w:     w,
+		h:     h,
 		x:     0,
 		y:     0,
-		vrow:  0,
 		lines: make([]string, 1),
 		ins:   NewInsert(),
 		mode:  ModeCommand,
@@ -67,21 +65,24 @@ func Init(args []string) *Editor {
 		bell:  false,
 	}
 
-	ed.Load()
+	if path != "" {
+		_, err := os.Stat(path)
+		if err == nil { // file exists
+			ed.Load(path)
+		}
+	}
 
 	termi.Raw()
 	return ed
 }
 
-func (ed *Editor) Save() {
-	if ed.path == "" {
-		return
-	}
+func (ed *Editor) Save(path string) {
 	text := strings.Join(ed.lines, "\n") + "\n"
-	err := os.WriteFile(ed.path, []byte(text), 0644)
+	err := os.WriteFile(path, []byte(text), 0644)
 	if err != nil {
 		panic(err)
 	}
+	ed.path = path
 }
 
 func (ed *Editor) Finish() {
@@ -90,16 +91,53 @@ func (ed *Editor) Finish() {
 	termi.Cooked()
 	termi.ShowCursor()
 
-	ed.Save()
+	if ed.path != "" {
+		ed.Save(ed.path)
+	}
+}
+
+func (ed *Editor) Line(row int) string {
+	if ed.mode == ModeInsert && row == ed.row {
+		return ed.ins.Line()
+	} else {
+		return ed.lines[row]
+	}
+}
+
+func (ed *Editor) CurrentLine() string {
+	return ed.Line(ed.row)
 }
 
 func (ed *Editor) RuneCount() int {
-	return utf8.RuneCountInString(ed.lines[ed.row])
+	return utf8.RuneCountInString(ed.CurrentLine())
+}
+
+func (ed *Editor) Confine() {
+	if ed.mode != ModeCommand {
+		panic("invalid state")
+	}
+
+	n := len(ed.lines)
+	if ed.row < 0 {
+		ed.row = 0
+	} else if ed.row >= n {
+		ed.row = max(n-1, 0)
+	}
+
+	rc := ed.RuneCount()
+	if ed.col < 0 {
+		ed.col = 0
+	} else if ed.col >= rc {
+		ed.col = max(rc-1, 0)
+	}
 }
 
 func (ed *Editor) InsertRune(r rune) {
-	ed.ins.Write(r)
-	ed.col++
+	if ed.mode != ModeInsert {
+		panic("invalid state")
+	}
+	ed.ins.WriteRune(r)
+	ed.col = ed.ins.Column()
 }
 
 func (ed *Editor) Ring() {
diff --git a/internal/editor/insert.go b/internal/editor/insert.go
index 82826f0..eb160fa 100644
--- a/internal/editor/insert.go
+++ b/internal/editor/insert.go
@@ -2,8 +2,6 @@ package editor
 
 import (
 	"unicode/utf8"
-
-	"tea.kareha.org/lab/termi"
 )
 
 type Insert struct {
@@ -31,11 +29,8 @@ func (ins *Insert) Reset() {
 	}
 }
 
-func (ins *Insert) Write(r rune) {
-	ins.body.WriteRune(r)
-}
-
-func (ins *Insert) Enter(line string, col int) {
+func (ins *Insert) Init(line string, col int) {
+	ins.Reset()
 	rs := []rune(line)
 	ins.head = string(rs[:col])
 	if col < len(rs) {
@@ -45,6 +40,10 @@ func (ins *Insert) Enter(line string, col int) {
 	}
 }
 
+func (ins *Insert) WriteRune(r rune) {
+	ins.body.WriteRune(r)
+}
+
 func (ins *Insert) Line() string {
 	return ins.head + ins.body.String() + ins.tail
 }
@@ -60,10 +59,9 @@ func (ins *Insert) Newline() []string {
 	return lines
 }
 
-func (ins *Insert) Width() int {
+func (ins *Insert) Column() int {
 	s := ins.head + ins.body.String()
-	rc := utf8.RuneCountInString(s)
-	return termi.StringWidth(s, rc)
+	return utf8.RuneCountInString(s)
 }
 
 func (ins *Insert) Backspace() bool {
diff --git a/internal/editor/main.go b/internal/editor/main.go
index e88d80b..485088e 100644
--- a/internal/editor/main.go
+++ b/internal/editor/main.go
@@ -5,6 +5,9 @@ import (
 )
 
 func (ed *Editor) ExitInsert() {
+	if ed.mode != ModeInsert {
+		panic("invalid state")
+	}
 	ed.lines[ed.row] = ed.ins.Line()
 	ed.ins.Reset()
 	ed.mode = ModeCommand
@@ -12,6 +15,9 @@ func (ed *Editor) ExitInsert() {
 }
 
 func (ed *Editor) InsertNewline() {
+	if ed.mode != ModeInsert {
+		panic("invalid state")
+	}
 	before := make([]string, 0, len(ed.lines)+1)
 	before = append(before, ed.lines[:ed.row]...)
 	var after []string
@@ -24,19 +30,24 @@ func (ed *Editor) InsertNewline() {
 	ed.lines = append(append(before, lines...), after...)
 	ed.row++
 	ed.col = 0
+	// row and col are confined automatically
 }
 
-func (ed *Editor) DeleteBefore() {
+func (ed *Editor) Backspace() {
+	if ed.mode != ModeInsert {
+		panic("invalid state")
+	}
 	if !ed.ins.Backspace() {
 		ed.Ring()
 		return
 	}
 	ed.col--
+	// col is confined automatically
 }
 
 func (ed *Editor) Main() {
 	for {
-		ed.Repaint()
+		ed.Draw()
 
 		key := termi.ReadKey()
 		switch ed.mode {
@@ -83,9 +94,9 @@ func (ed *Editor) Main() {
 				case termi.RuneEnter:
 					ed.InsertNewline()
 				case termi.RuneBackspace:
-					ed.DeleteBefore()
+					ed.Backspace()
 				case termi.RuneDelete:
-					ed.DeleteBefore()
+					ed.Backspace()
 				default:
 					ed.InsertRune(key.Rune)
 				}
diff --git a/internal/editor/view.go b/internal/editor/view.go
index 598d7bc..e6b877c 100644
--- a/internal/editor/view.go
+++ b/internal/editor/view.go
@@ -7,34 +7,26 @@ import (
 )
 
 func (ed *Editor) LineHeight(line string) int {
-	w, _ := termi.Size()
 	rc := utf8.RuneCountInString(line)
 	width := termi.StringWidth(line, rc)
-	return 1 + max(width-1, 0)/w
+	return 1 + max(width-1, 0)/ed.w
 }
 
 func (ed *Editor) DrawBuffer() {
-	_, h := termi.Size()
-
 	y := 0
 	for i := ed.vrow; i < len(ed.lines); i++ {
-		var line string
-		if ed.mode == ModeInsert && i == ed.row {
-			line = ed.ins.Line()
-		} else {
-			line = ed.lines[i]
-		}
+		line := ed.Line(i)
 
 		termi.MoveCursor(0, y)
 		termi.Draw(line)
 
 		y += ed.LineHeight(line)
-		if y >= h-1 {
+		if y >= ed.h-1 {
 			break
 		}
 	}
 
-	for ; y < h-1; y++ {
+	for ; y < ed.h-1; y++ {
 		termi.MoveCursor(0, y)
 		termi.Draw("~")
 	}
@@ -49,8 +41,7 @@ func (ed *Editor) DrawStatus() {
 		m = "i"
 	}
 
-	_, h := termi.Size()
-	termi.MoveCursor(0, h-1)
+	termi.MoveCursor(0, ed.h-1)
 	if ed.bell {
 		termi.EnableInvert()
 	}
@@ -62,25 +53,10 @@ func (ed *Editor) DrawStatus() {
 }
 
 func (ed *Editor) UpdateCursor() {
-	w, h := termi.Size()
-
-	var dy int
-	switch ed.mode {
-	case ModeCommand:
-		ed.row = min(max(ed.row, 0), max(len(ed.lines)-1, 0))
-		len := ed.RuneCount()
-		ed.col = min(ed.col, max(len-1, 0))
-
-		// XXX approximation
-		width := termi.StringWidth(ed.lines[ed.row], ed.col)
-		ed.x = width % w
-		dy = width / w
-	case ModeInsert:
-		// XXX approximation
-		width := ed.ins.Width()
-		ed.x = width % w
-		dy = width / w
-	}
+	// XXX approximation
+	width := termi.StringWidth(ed.CurrentLine(), ed.col)
+	ed.x = width % ed.w
+	dy := width / ed.w
 
 	if ed.row < ed.vrow {
 		ed.vrow = ed.row
@@ -92,7 +68,7 @@ func (ed *Editor) UpdateCursor() {
 	}
 	ed.y = y + dy
 
-	for ed.y >= h-1 {
+	for ed.y >= ed.h-1 {
 		ed.vrow++
 
 		y := 0
@@ -104,6 +80,10 @@ func (ed *Editor) UpdateCursor() {
 }
 
 func (ed *Editor) Repaint() {
+	w, h := termi.Size()
+	ed.w = w
+	ed.h = h
+
 	termi.HideCursor()
 
 	termi.Clear()
@@ -118,3 +98,7 @@ func (ed *Editor) Repaint() {
 
 	termi.ShowCursor()
 }
+
+func (ed *Editor) Draw() {
+	ed.Repaint()
+}