diff --git a/example/blocks/field.go b/example/blocks/field.go
index 3df2482b3..7e43531eb 100644
--- a/example/blocks/field.go
+++ b/example/blocks/field.go
@@ -93,7 +93,7 @@ func (f *Field) Flush() {
 	}
 }
 
-func (f *Field) Draw(context graphics.Context, textures *Textures, geo matrix.Geometry) {
+func (f *Field) Draw(context graphics.Context, textures Textures, geo matrix.Geometry) {
 	blocks := make([][]BlockType, len(f.blocks))
 	for i, blockCol := range f.blocks {
 		blocks[i] = make([]BlockType, len(blockCol))
diff --git a/example/blocks/font.go b/example/blocks/font.go
index 506b00e0b..5acb1dc98 100644
--- a/example/blocks/font.go
+++ b/example/blocks/font.go
@@ -19,7 +19,7 @@ func textWidth(str string) int {
 
 func drawText(
 	context graphics.Context,
-	textures *Textures,
+	textures Textures,
 	str string,
 	x, y, scale int,
 	clr color.Color) {
@@ -55,7 +55,7 @@ func drawText(
 
 func drawTextWithShadow(
 	context graphics.Context,
-	textures *Textures,
+	textures Textures,
 	str string,
 	x, y, scale int,
 	clr color.Color) {
diff --git a/example/blocks/game.go b/example/blocks/game.go
index bdded8273..06b1b6b24 100644
--- a/example/blocks/game.go
+++ b/example/blocks/game.go
@@ -23,17 +23,25 @@ type GameState struct {
 	Input        *Input
 }
 
+type Textures interface {
+	RequestTexture(name string, path string)
+	RequestRenderTarget(name string, size Size)
+	Has(name string) bool
+	GetTexture(name string) graphics.TextureId
+	GetRenderTarget(name string) graphics.RenderTargetId
+}
+
 type Game struct {
 	sceneManager *SceneManager
 	input        *Input
-	textures     *Textures
+	textures     Textures
 }
 
-func NewGame(textureFactory graphics.TextureFactory) *Game {
+func NewGame(textures Textures) *Game {
 	game := &Game{
 		sceneManager: NewSceneManager(NewTitleScene()),
 		input:        NewInput(),
-		textures:     NewTextures(textureFactory),
+		textures:     textures,
 	}
 	for name, path := range texturePaths {
 		game.textures.RequestTexture(name, path)
diff --git a/example/blocks/game_scene.go b/example/blocks/game_scene.go
index 039c35e93..c919b2074 100644
--- a/example/blocks/game_scene.go
+++ b/example/blocks/game_scene.go
@@ -97,7 +97,7 @@ func (s *GameScene) Update(state *GameState) {
 	}
 }
 
-func (s *GameScene) Draw(context graphics.Context, textures *Textures) {
+func (s *GameScene) Draw(context graphics.Context, textures Textures) {
 	context.Fill(0xff, 0xff, 0xff)
 
 	field := textures.GetTexture("empty")
diff --git a/example/blocks/piece.go b/example/blocks/piece.go
index 31d8c68b0..613a741fd 100644
--- a/example/blocks/piece.go
+++ b/example/blocks/piece.go
@@ -125,7 +125,7 @@ const fieldBlockNumY = 20
 
 func drawBlocks(
 	context graphics.Context,
-	textures *Textures,
+	textures Textures,
 	blocks [][]BlockType,
 	geo matrix.Geometry) {
 	parts := []graphics.TexturePart{}
@@ -211,7 +211,7 @@ func (p *Piece) AbsorbInto(field *Field, x, y int, angle Angle) {
 
 func (p *Piece) Draw(
 	context graphics.Context,
-	textures *Textures,
+	textures Textures,
 	fieldX, fieldY int,
 	pieceX, pieceY int,
 	angle Angle) {
diff --git a/example/blocks/scene_manager.go b/example/blocks/scene_manager.go
index b944cc104..ad288ee90 100644
--- a/example/blocks/scene_manager.go
+++ b/example/blocks/scene_manager.go
@@ -14,7 +14,7 @@ func init() {
 
 type Scene interface {
 	Update(state *GameState)
-	Draw(context graphics.Context, textures *Textures)
+	Draw(context graphics.Context, textures Textures)
 }
 
 const transitionMaxCount = 20
@@ -45,7 +45,7 @@ func (s *SceneManager) Update(state *GameState) {
 	}
 }
 
-func (s *SceneManager) Draw(context graphics.Context, textures *Textures) {
+func (s *SceneManager) Draw(context graphics.Context, textures Textures) {
 	if s.transitionCount == -1 {
 		s.current.Draw(context, textures)
 		return
diff --git a/example/blocks/title_scene.go b/example/blocks/title_scene.go
index 3f1adcfba..87d2a5921 100644
--- a/example/blocks/title_scene.go
+++ b/example/blocks/title_scene.go
@@ -26,7 +26,7 @@ func (s *TitleScene) Update(state *GameState) {
 	}
 }
 
-func (s *TitleScene) Draw(context graphics.Context, textures *Textures) {
+func (s *TitleScene) Draw(context graphics.Context, textures Textures) {
 	drawTitleBackground(context, textures, s.count)
 	drawLogo(context, textures, "BLOCKS")
 
@@ -36,7 +36,7 @@ func (s *TitleScene) Draw(context graphics.Context, textures *Textures) {
 	drawTextWithShadow(context, textures, message, x, y, 1, color.RGBA{0x80, 0, 0, 0xff})
 }
 
-func drawTitleBackground(context graphics.Context, textures *Textures, c int) {
+func drawTitleBackground(context graphics.Context, textures Textures, c int) {
 	const textureWidth = 32
 	const textureHeight = 32
 
@@ -60,7 +60,7 @@ func drawTitleBackground(context graphics.Context, textures *Textures, c int) {
 	context.Texture(backgroundTextureId).Draw(parts, geo, clr)
 }
 
-func drawLogo(context graphics.Context, textures *Textures, str string) {
+func drawLogo(context graphics.Context, textures Textures, str string) {
 	scale := 4
 	textWidth := textWidth(str) * scale
 	x := (ScreenWidth - textWidth) / 2
diff --git a/example/main.go b/example/main.go
index 2b867e790..8aa703d1c 100644
--- a/example/main.go
+++ b/example/main.go
@@ -30,7 +30,6 @@ func main() {
 	const title = "Ebiten Demo"
 
 	u := cocoa.UI()
-	textureFactory := cocoa.TextureFactory()
 	window := u.CreateGameWindow(screenWidth, screenHeight, screenScale, title)
 
 	drawing := make(chan struct{})
@@ -39,7 +38,8 @@ func main() {
 		defer close(quit)
 
 		windowEvents := window.Events()
-		var game Game = blocks.NewGame(textureFactory)
+		textureFactory := cocoa.TextureFactory()
+		var game Game = blocks.NewGame(NewTextures(textureFactory))
 		frameTime := time.Duration(int64(time.Second) / int64(fps))
 		tick := time.Tick(frameTime)
 		for {
diff --git a/example/blocks/textures.go b/example/textures.go
similarity index 93%
rename from example/blocks/textures.go
rename to example/textures.go
index 38e4ccf4d..cf7f0f6f0 100644
--- a/example/blocks/textures.go
+++ b/example/textures.go
@@ -1,6 +1,7 @@
-package blocks
+package main
 
 import (
+	"github.com/hajimehoshi/go-ebiten/example/blocks"
 	"github.com/hajimehoshi/go-ebiten/graphics"
 	"image"
 	"os"
@@ -14,7 +15,7 @@ type namePath struct {
 
 type nameSize struct {
 	name string
-	size Size
+	size blocks.Size
 }
 
 type Textures struct {
@@ -98,7 +99,7 @@ func (t *Textures) RequestTexture(name string, path string) {
 	t.texturePaths <- namePath{name, path}
 }
 
-func (t *Textures) RequestRenderTarget(name string, size Size) {
+func (t *Textures) RequestRenderTarget(name string, size blocks.Size) {
 	t.renderTargetSizes <- nameSize{name, size}
 }
 
diff --git a/graphics/opengl/ids.go b/graphics/opengl/ids.go
index 1c1ba2a02..d7e988aa8 100644
--- a/graphics/opengl/ids.go
+++ b/graphics/opengl/ids.go
@@ -35,7 +35,7 @@ type ids struct {
 	textures              map[graphics.TextureId]*Texture
 	renderTargets         map[graphics.RenderTargetId]*RenderTarget
 	renderTargetToTexture map[graphics.RenderTargetId]graphics.TextureId
-	counts                chan int
+	lastId                int
 	currentRenderTargetId graphics.RenderTargetId
 	sync.RWMutex
 }
@@ -45,14 +45,9 @@ func newIds() *ids {
 		textures:              map[graphics.TextureId]*Texture{},
 		renderTargets:         map[graphics.RenderTargetId]*RenderTarget{},
 		renderTargetToTexture: map[graphics.RenderTargetId]graphics.TextureId{},
-		counts:                make(chan int),
+		lastId:                0,
 		currentRenderTargetId: -1,
 	}
-	go func() {
-		for i := 1; ; i++ {
-			ids.counts <- i
-		}
-	}()
 	return ids
 }
 
@@ -80,10 +75,11 @@ func (i *ids) createTexture(img image.Image, filter graphics.Filter) (
 	if err != nil {
 		return 0, err
 	}
-	textureId := graphics.TextureId(<-i.counts)
 
 	i.Lock()
 	defer i.Unlock()
+	i.lastId++
+	textureId := graphics.TextureId(i.lastId)
 	i.textures[textureId] = texture
 	return textureId, nil
 }
@@ -100,11 +96,13 @@ func (i *ids) createRenderTarget(width, height int, filter graphics.Filter) (
 	i.currentRenderTargetId = -1
 	renderTarget := &RenderTarget{framebuffer, texture.width, texture.height, false}
 
-	textureId := graphics.TextureId(<-i.counts)
-	renderTargetId := graphics.RenderTargetId(<-i.counts)
-
 	i.Lock()
 	defer i.Unlock()
+	i.lastId++
+	textureId := graphics.TextureId(i.lastId)
+	i.lastId++
+	renderTargetId := graphics.RenderTargetId(i.lastId)
+
 	i.textures[textureId] = texture
 	i.renderTargets[renderTargetId] = renderTarget
 	i.renderTargetToTexture[renderTargetId] = textureId
@@ -114,10 +112,10 @@ func (i *ids) createRenderTarget(width, height int, filter graphics.Filter) (
 
 // NOTE: renderTarget can't be used as a texture.
 func (i *ids) addRenderTarget(renderTarget *RenderTarget) graphics.RenderTargetId {
-	id := graphics.RenderTargetId(<-i.counts)
-
 	i.Lock()
 	defer i.Unlock()
+	i.lastId++
+	id := graphics.RenderTargetId(i.lastId)
 	i.renderTargets[id] = renderTarget
 
 	return id
diff --git a/graphics/opengl/shader/draw_texture.go b/graphics/opengl/shader/draw_texture.go
index 536dfd8f9..77608c578 100644
--- a/graphics/opengl/shader/draw_texture.go
+++ b/graphics/opengl/shader/draw_texture.go
@@ -27,7 +27,6 @@ func DrawTexture(native NativeTexture, projectionMatrix [16]float32,
 	}
 	// TODO: Check performance
 	shaderProgram := use(projectionMatrix, geometryMatrix, colorMatrix)
-	defer C.glUseProgram(0)
 
 	C.glBindTexture(C.GL_TEXTURE_2D, C.GLuint(native))
 	defer C.glBindTexture(C.GL_TEXTURE_2D, 0)
diff --git a/graphics/opengl/shader/program.go b/graphics/opengl/shader/program.go
index be15a9370..fde2c4e1b 100644
--- a/graphics/opengl/shader/program.go
+++ b/graphics/opengl/shader/program.go
@@ -23,6 +23,7 @@ const (
 )
 
 var programs = map[programId]*program{
+	// TODO: programRegular is not used for now. Remove this.
 	programRegular: &program{
 		shaderIds: []shaderId{shaderVertex, shaderFragment},
 	},
@@ -115,11 +116,9 @@ func getUniformLocation(program C.GLuint, name string) C.GLint {
 func use(projectionMatrix [16]float32,
 	geometryMatrix matrix.Geometry,
 	colorMatrix matrix.Color) C.GLuint {
-	programId := programRegular
-	if !colorMatrix.IsIdentity() {
-		programId = programColorMatrix
-	}
+	programId :=  programColorMatrix
 	program := programs[programId]
+	// TODO: Check the performance.
 	C.glUseProgram(program.native)
 
 	C.glUniformMatrix4fv(C.GLint(getUniformLocation(program.native, "projection_matrix")),
@@ -143,10 +142,6 @@ func use(projectionMatrix [16]float32,
 
 	C.glUniform1i(getUniformLocation(program.native, "texture"), 0)
 
-	if programId != programColorMatrix {
-		return program.native
-	}
-
 	e := [4][5]float32{}
 	for i := 0; i < 4; i++ {
 		for j := 0; j < 5; j++ {