diff --git a/ebiten.go b/ebiten.go
index d16099431..7d2f26226 100644
--- a/ebiten.go
+++ b/ebiten.go
@@ -3,19 +3,20 @@ package ebiten
 import (
 	"time"
 	"github.com/hajimehoshi/go-ebiten/graphics"
+	"github.com/hajimehoshi/go-ebiten/graphics/opengl"
 	"github.com/hajimehoshi/go-ebiten/ui"
 )
 
 type Game interface {
 	Update()
-	Draw(g *graphics.GraphicsContext, offscreen *graphics.Texture)
+	Draw(g graphics.GraphicsContext, offscreen graphics.Texture)
 }
 
 func Run(game Game, u ui.UI) {
 	ch := make(chan bool, 1)
-	device := graphics.NewDevice(
+	device := opengl.NewDevice(
 		u.ScreenWidth(), u.ScreenHeight(), u.ScreenScale(),
-		func(g *graphics.GraphicsContext, offscreen *graphics.Texture) {
+		func(g graphics.GraphicsContext, offscreen graphics.Texture) {
 			ticket := <-ch
 			game.Draw(g, offscreen)
 			ch<- ticket
diff --git a/examples/glut/main.go b/examples/glut/main.go
index 9aaa7be84..3d93ca7db 100644
--- a/examples/glut/main.go
+++ b/examples/glut/main.go
@@ -28,7 +28,7 @@ type GlutUI struct{
 	screenWidth int
 	screenHeight int
 	screenScale int
-	device *graphics.Device
+	device graphics.Device
 }
 
 var currentUI *GlutUI
@@ -85,13 +85,13 @@ func (ui *GlutUI) ScreenScale() int {
 	return ui.screenScale
 }
 
-func (ui *GlutUI) Run(device *graphics.Device) {
+func (ui *GlutUI) Run(device graphics.Device) {
 	ui.device = device
 	C.glutMainLoop()
 }
 
 type DemoGame struct {
-	ebitenTexture *graphics.Texture
+	ebitenTexture graphics.Texture
 	x int
 }
 
@@ -108,12 +108,13 @@ func (game *DemoGame) Update() {
 			panic(err)
 		}
 
+		// TODO: It looks strange to get a texture from the device.
 		game.ebitenTexture = currentUI.device.NewTextureFromImage(img)
 	}
 	game.x++
 }
 
-func (game *DemoGame) Draw(g *graphics.GraphicsContext, offscreen *graphics.Texture) {
+func (game *DemoGame) Draw(g graphics.GraphicsContext, offscreen graphics.Texture) {
 	g.Fill(&color.RGBA{R: 128, G: 128, B: 255, A: 255})
 	if game.ebitenTexture == nil {
 		return
@@ -122,7 +123,7 @@ func (game *DemoGame) Draw(g *graphics.GraphicsContext, offscreen *graphics.Text
 	geometryMatrix.SetTx(graphics.AffineMatrixElement(game.x))
 	geometryMatrix.SetTy(graphics.AffineMatrixElement(game.x))
 	g.DrawTexture(game.ebitenTexture,
-		0, 0, game.ebitenTexture.Width, game.ebitenTexture.Height,
+		0, 0, game.ebitenTexture.Width(), game.ebitenTexture.Height(),
 		geometryMatrix,
 		graphics.IdentityColorMatrix())
 }
diff --git a/graphics/graphics.go b/graphics/graphics.go
new file mode 100644
index 000000000..f3ce2a4bd
--- /dev/null
+++ b/graphics/graphics.go
@@ -0,0 +1,29 @@
+package graphics
+
+import (
+	"image"
+	"image/color"
+)
+
+type Device interface {
+	Update()
+	// TODO: Move somewhere
+	NewTexture(width, height int) Texture
+	NewTextureFromImage(img image.Image) Texture
+}
+
+type GraphicsContext interface {
+	Clear()
+	Fill(color color.Color)
+	DrawTexture(texture Texture,
+		srcX, srcY, srcWidth, srcHeight int,
+		geometryMatrix *GeometryMatrix, colorMatrix *ColorMatrix)
+	SetOffscreen(texture Texture)
+}
+
+type Texture interface {
+	Width() int
+	Height() int
+	TextureWidth() int
+	TextureHeight() int
+}
diff --git a/graphics/device.go b/graphics/opengl/device.go
similarity index 74%
rename from graphics/device.go
rename to graphics/opengl/device.go
index 5398c28aa..9e3223af7 100644
--- a/graphics/device.go
+++ b/graphics/opengl/device.go
@@ -1,4 +1,4 @@
-package graphics
+package opengl
 
 // #cgo LDFLAGS: -framework OpenGL
 //
@@ -7,6 +7,7 @@ package graphics
 import "C"
 import (
 	"image"
+	"github.com/hajimehoshi/go-ebiten/graphics"
 )
 
 type Device struct {
@@ -15,12 +16,12 @@ type Device struct {
 	screenScale int
 	graphicsContext *GraphicsContext
 	offscreenTexture *Texture
-	drawFunc func(*GraphicsContext, *Texture)
+	drawFunc func(graphics.GraphicsContext, graphics.Texture)
 	funcs []func()
 }
 
 func NewDevice(screenWidth, screenHeight, screenScale int,
-	drawFunc func(*GraphicsContext, *Texture)) *Device {
+	drawFunc func(graphics.GraphicsContext, graphics.Texture)) *Device {
 	device := &Device{
 		screenWidth: screenWidth,
 		screenHeight: screenHeight,
@@ -29,7 +30,7 @@ func NewDevice(screenWidth, screenHeight, screenScale int,
 		drawFunc: drawFunc,
 		funcs: []func(){},
 	}
-	device.offscreenTexture = device.NewTexture(screenWidth, screenHeight)
+	device.offscreenTexture = device.NewTexture(screenWidth, screenHeight).(*Texture)
 	return device
 }
 
@@ -52,20 +53,20 @@ func (device *Device) Update() {
 	C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MAG_FILTER, C.GL_LINEAR)
 	g.resetOffscreen()
 	g.Clear()
-	geometryMatrix := IdentityGeometryMatrix()
-	geometryMatrix.SetA(AffineMatrixElement(g.screenScale))
-	geometryMatrix.SetD(AffineMatrixElement(g.screenScale))
+	geometryMatrix := graphics.IdentityGeometryMatrix()
+	geometryMatrix.SetA(graphics.AffineMatrixElement(g.screenScale))
+	geometryMatrix.SetD(graphics.AffineMatrixElement(g.screenScale))
 	g.DrawTexture(device.offscreenTexture,
 		0, 0, device.screenWidth, device.screenHeight,
-		geometryMatrix, IdentityColorMatrix())
+		geometryMatrix, graphics.IdentityColorMatrix())
 	g.flush()
 }
 
-func (device *Device) NewTexture(width, height int) *Texture {
+func (device *Device) NewTexture(width, height int) graphics.Texture {
 	return createTexture(device, width, height, nil)
 }
 
-func (device *Device) NewTextureFromImage(img image.Image) *Texture {
+func (device *Device) NewTextureFromImage(img image.Image) graphics.Texture {
 	var pix []uint8
 	switch img.(type) {
 	case *image.RGBA:
diff --git a/graphics/graphics_context.go b/graphics/opengl/graphics_context.go
similarity index 88%
rename from graphics/graphics_context.go
rename to graphics/opengl/graphics_context.go
index 2185632d6..616912232 100644
--- a/graphics/graphics_context.go
+++ b/graphics/opengl/graphics_context.go
@@ -1,4 +1,4 @@
-package graphics
+package opengl
 
 // #cgo LDFLAGS: -framework OpenGL
 //
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"image/color"
 	"unsafe"
+	"github.com/hajimehoshi/go-ebiten/graphics"
 )
 
 type GraphicsContext struct {
@@ -45,8 +46,8 @@ func (context *GraphicsContext) Clear() {
 	C.glClear(C.GL_COLOR_BUFFER_BIT)
 }
 
-func (context *GraphicsContext) Fill(color color.Color) {
-	r, g, b, a := color.RGBA()
+func (context *GraphicsContext) Fill(clr color.Color) {
+	r, g, b, a := clr.RGBA()
 	max := 65535.0
 	C.glClearColor(
 		C.GLclampf(float64(r) / max),
@@ -56,16 +57,18 @@ func (context *GraphicsContext) Fill(color color.Color) {
 	C.glClear(C.GL_COLOR_BUFFER_BIT)
 }
 
-func (context *GraphicsContext) DrawRect(x, y, width, height int, color color.Color) {
+func (context *GraphicsContext) DrawRect(x, y, width, height int, clr color.Color) {
 	// TODO: implement!
 }
 
-func (context *GraphicsContext) DrawTexture(texture *Texture,
+func (context *GraphicsContext) DrawTexture(tex graphics.Texture,
 	srcX, srcY, srcWidth, srcHeight int,
-	geometryMatrix *GeometryMatrix, colorMatrix *ColorMatrix) {
+	geometryMatrix *graphics.GeometryMatrix, colorMatrix *graphics.ColorMatrix) {
 	geometryMatrix = geometryMatrix.Clone()
 	colorMatrix    = colorMatrix.Clone()
 
+	texture := tex.(*Texture)
+
 	context.setShaderProgram(geometryMatrix, colorMatrix)
 	C.glBindTexture(C.GL_TEXTURE_2D, texture.id)
 
@@ -80,10 +83,10 @@ func (context *GraphicsContext) DrawTexture(texture *Texture,
 		x2, y2,
 	}
 
-	tu1 := float32(srcX)             / float32(texture.TextureWidth)
-	tu2 := float32(srcX + srcWidth)  / float32(texture.TextureWidth)
-	tv1 := float32(srcY)             / float32(texture.TextureHeight)
-	tv2 := float32(srcY + srcHeight) / float32(texture.TextureHeight)
+	tu1 := float32(srcX)             / float32(texture.textureWidth)
+	tu2 := float32(srcX + srcWidth)  / float32(texture.textureWidth)
+	tv1 := float32(srcY)             / float32(texture.textureHeight)
+	tv2 := float32(srcY + srcHeight) / float32(texture.textureHeight)
 	texCoord := [...]float32{
 		tu1, tv1,
 		tu2, tv1,
@@ -116,7 +119,12 @@ func abs(x int) int {
 	return x
 }
 
-func (context *GraphicsContext) SetOffscreen(texture *Texture) {
+func (context *GraphicsContext) SetOffscreen(tex graphics.Texture) {
+	var texture *Texture = nil
+	if tex != nil {
+		texture = tex.(*Texture)
+	}
+	// TODO: glFlush() here?
 	framebuffer := C.GLuint(0)
 	if texture != nil {
 		framebuffer = context.getFramebuffer(texture)
@@ -135,8 +143,8 @@ func (context *GraphicsContext) SetOffscreen(texture *Texture) {
 
 	width, height, tx, ty := 0, 0, 0, 0
 	if framebuffer != context.mainFramebuffer {
-		width  = texture.TextureWidth
-		height = texture.TextureHeight
+		width  = texture.textureWidth
+		height = texture.textureHeight
 		tx     = -1
 		ty     = -1
 	} else {
@@ -169,7 +177,7 @@ func (context *GraphicsContext) flush() {
 
 // This method should be called on the UI thread.
 func (context *GraphicsContext) setShaderProgram(
-	geometryMatrix *GeometryMatrix, colorMatrix *ColorMatrix) {
+	geometryMatrix *graphics.GeometryMatrix, colorMatrix *graphics.ColorMatrix) {
 	program := C.GLuint(0)
 	if colorMatrix.IsIdentity() {
 		program = regularShaderProgram
diff --git a/graphics/shader.go b/graphics/opengl/shader.go
similarity index 99%
rename from graphics/shader.go
rename to graphics/opengl/shader.go
index 5510ac7d3..1a10db11c 100644
--- a/graphics/shader.go
+++ b/graphics/opengl/shader.go
@@ -1,4 +1,4 @@
-package graphics
+package opengl
 
 // #cgo LDFLAGS: -framework OpenGL
 //
diff --git a/graphics/texture.go b/graphics/opengl/texture.go
similarity index 76%
rename from graphics/texture.go
rename to graphics/opengl/texture.go
index 8840ad0bc..567da56a1 100644
--- a/graphics/texture.go
+++ b/graphics/opengl/texture.go
@@ -1,4 +1,4 @@
-package graphics
+package opengl
 
 // #cgo LDFLAGS: -framework OpenGL
 //
@@ -21,10 +21,10 @@ func Clp2(x uint64) uint64 {
 
 type Texture struct {
 	id C.GLuint
-	Width int
-	Height int
-	TextureWidth int
-	TextureHeight int
+	width int
+	height int
+	textureWidth int
+	textureHeight int
 }
 
 func createTexture(device *Device, width, height int, pixels []uint8) *Texture{
@@ -40,10 +40,10 @@ func createTexture(device *Device, width, height int, pixels []uint8) *Texture{
 	}
 	texture := &Texture{
 		id: 0,
-		Width: width,
-		Height: height,
-		TextureWidth: textureWidth,
-		TextureHeight: textureHeight,
+		width: width,
+		height: height,
+		textureWidth: textureWidth,
+		textureHeight: textureHeight,
 	}
 
 	device.executeWhenDrawing(func() {
@@ -74,6 +74,22 @@ func createTexture(device *Device, width, height int, pixels []uint8) *Texture{
 	return texture
 }
 
+func (texture *Texture) Width() int {
+	return texture.width
+}
+
+func (texture *Texture) Height() int {
+	return texture.height
+}
+
+func (texture *Texture) TextureWidth() int {
+	return texture.textureWidth
+}
+
+func (texture *Texture) TextureHeight() int {
+	return texture.textureHeight
+}
+
 func (texture *Texture) IsAvailable() bool {
 	return texture.id != 0
 }
diff --git a/graphics/texture_test.go b/graphics/opengl/texture_test.go
similarity index 94%
rename from graphics/texture_test.go
rename to graphics/opengl/texture_test.go
index f068b215b..13b64a156 100644
--- a/graphics/texture_test.go
+++ b/graphics/opengl/texture_test.go
@@ -1,4 +1,4 @@
-package graphics_test
+package opengl_test
 
 import (
 	"testing"
diff --git a/ui/ui.go b/ui/ui.go
index a0e1b56f6..58cc5101e 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -8,5 +8,5 @@ type UI interface {
 	ScreenWidth() int
 	ScreenHeight() int
 	ScreenScale() int
-	Run(device *graphics.Device)
+	Run(device graphics.Device)
 }