diff --git a/gamecontext.go b/gamecontext.go
index d98b365d8..7cbdac365 100644
--- a/gamecontext.go
+++ b/gamecontext.go
@@ -15,30 +15,60 @@
 package ebiten
 
 import (
+	"github.com/hajimehoshi/ebiten/internal/graphics"
+	"github.com/hajimehoshi/ebiten/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/ui"
 	"image"
 )
 
 // IsKeyPressed returns a boolean indicating whether key is pressed.
 func IsKeyPressed(key Key) bool {
-	return currentUI.input.isKeyPressed(key)
+	return ui.Current().Input().IsKeyPressed(ui.Key(key))
 }
 
 // CursorPosition returns a position of a mouse cursor.
 func CursorPosition() (x, y int) {
-	return currentUI.input.cursorPosition()
+	return ui.Current().Input().CursorPosition()
 }
 
 // IsMouseButtonPressed returns a boolean indicating whether mouseButton is pressed.
 func IsMouseButtonPressed(mouseButton MouseButton) bool {
-	return currentUI.input.isMouseButtonPressed(mouseButton)
+	return ui.Current().Input().IsMouseButtonPressed(ui.MouseButton(mouseButton))
 }
 
 // NewImage returns an empty image.
 func NewImage(width, height int, filter Filter) (*Image, error) {
-	return currentUI.newImage(width, height, filter)
+	var innerImage *innerImage
+	var err error
+	ui.Current().Use(func(c *opengl.Context) {
+		var texture *graphics.Texture
+		texture, err = graphics.NewTexture(c, width, height, glFilter(c, filter))
+		if err != nil {
+			return
+		}
+		innerImage, err = newInnerImage(c, texture)
+		innerImage.Clear(c)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &Image{ui: ui.Current(), inner: innerImage}, nil
 }
 
 // NewImageFromImage creates a new image with the given image (img).
 func NewImageFromImage(img image.Image, filter Filter) (*Image, error) {
-	return currentUI.newImageFromImage(img, filter)
+	var innerImage *innerImage
+	var err error
+	ui.Current().Use(func(c *opengl.Context) {
+		var texture *graphics.Texture
+		texture, err = graphics.NewTextureFromImage(c, img, glFilter(c, filter))
+		if err != nil {
+			return
+		}
+		innerImage, err = newInnerImage(c, texture)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &Image{ui: ui.Current(), inner: innerImage}, nil
 }
diff --git a/graphicscontext.go b/graphicscontext.go
index 027c7e7d0..fd5268a2e 100644
--- a/graphicscontext.go
+++ b/graphicscontext.go
@@ -34,13 +34,12 @@ func newGraphicsContext(c *opengl.Context, screenWidth, screenHeight, screenScal
 		return nil, err
 	}
 
-	gc := &graphicsContext{
+	return &graphicsContext{
 		glContext:   c,
 		defaultR:    &innerImage{f, nil},
 		screen:      screen,
 		screenScale: screenScale,
-	}
-	return gc, nil
+	}, nil
 }
 
 type graphicsContext struct {
diff --git a/image.go b/image.go
index 6022d507f..ba520fc35 100644
--- a/image.go
+++ b/image.go
@@ -18,6 +18,7 @@ import (
 	"github.com/hajimehoshi/ebiten/internal"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/ui"
 	"image"
 	"image/color"
 )
@@ -102,7 +103,7 @@ func (t *textureQuads) Texture(i int) (u0, v0, u1, v1 float32) {
 // The pixel format is alpha-premultiplied.
 // Image implements image.Image.
 type Image struct {
-	ui     *ui
+	ui     *ui.UI
 	inner  *innerImage
 	pixels []uint8
 }
@@ -115,8 +116,8 @@ func (i *Image) Size() (width, height int) {
 // Clear resets the pixels of the image into 0.
 func (i *Image) Clear() (err error) {
 	i.pixels = nil
-	i.ui.use(func() {
-		err = i.inner.Clear(i.ui.glContext)
+	i.ui.Use(func(c *opengl.Context) {
+		err = i.inner.Clear(c)
 	})
 	return
 }
@@ -124,8 +125,8 @@ func (i *Image) Clear() (err error) {
 // Fill fills the image with a solid color.
 func (i *Image) Fill(clr color.Color) (err error) {
 	i.pixels = nil
-	i.ui.use(func() {
-		err = i.inner.Fill(i.ui.glContext, clr)
+	i.ui.Use(func(c *opengl.Context) {
+		err = i.inner.Fill(c, clr)
 	})
 	return
 }
@@ -147,8 +148,8 @@ func (i *Image) DrawImage(image *Image, options *DrawImageOptions) (err error) {
 
 func (i *Image) drawImage(image *innerImage, option *DrawImageOptions) (err error) {
 	i.pixels = nil
-	i.ui.use(func() {
-		err = i.inner.drawImage(i.ui.glContext, image, option)
+	i.ui.Use(func(c *opengl.Context) {
+		err = i.inner.drawImage(c, image, option)
 	})
 	return
 }
@@ -169,9 +170,9 @@ func (i *Image) ColorModel() color.Model {
 // This method loads pixels from GPU to VRAM if necessary.
 func (i *Image) At(x, y int) color.Color {
 	if i.pixels == nil {
-		i.ui.use(func() {
+		i.ui.Use(func(c *opengl.Context) {
 			var err error
-			i.pixels, err = i.inner.texture.Pixels(i.ui.glContext)
+			i.pixels, err = i.inner.texture.Pixels(c)
 			if err != nil {
 				panic(err)
 			}
diff --git a/input.go b/internal/ui/input.go
similarity index 77%
rename from input.go
rename to internal/ui/input.go
index 68f663c38..7edc372d5 100644
--- a/input.go
+++ b/internal/ui/input.go
@@ -1,4 +1,4 @@
-// Copyright 2014 Hajime Hoshi
+// Copyright 2015 Hajime Hoshi
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,13 +12,33 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package ebiten
+package ui
 
 import (
 	glfw "github.com/go-gl/glfw3"
 	"math"
 )
 
+type Key int
+
+const (
+	KeyUp Key = iota
+	KeyDown
+	KeyLeft
+	KeyRight
+	KeySpace
+	KeyMax
+)
+
+type MouseButton int
+
+const (
+	MouseButtonLeft MouseButton = iota
+	MouseButtonRight
+	MouseButtonMiddle
+	MouseButtonMax
+)
+
 type input struct {
 	keyPressed         [KeyMax]bool
 	mouseButtonPressed [MouseButtonMax]bool
@@ -26,15 +46,15 @@ type input struct {
 	cursorY            int
 }
 
-func (i *input) isKeyPressed(key Key) bool {
+func (i *input) IsKeyPressed(key Key) bool {
 	return i.keyPressed[key]
 }
 
-func (i *input) isMouseButtonPressed(button MouseButton) bool {
+func (i *input) IsMouseButtonPressed(button MouseButton) bool {
 	return i.mouseButtonPressed[button]
 }
 
-func (i *input) cursorPosition() (x, y int) {
+func (i *input) CursorPosition() (x, y int) {
 	return i.cursorX, i.cursorY
 }
 
diff --git a/ui.go b/internal/ui/ui.go
similarity index 53%
rename from ui.go
rename to internal/ui/ui.go
index 472287d61..3b852a114 100644
--- a/ui.go
+++ b/internal/ui/ui.go
@@ -1,4 +1,4 @@
-// Copyright 2014 Hajime Hoshi
+// Copyright 2015 Hajime Hoshi
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,18 +12,20 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package ebiten
+package ui
 
 import (
 	"fmt"
 	glfw "github.com/go-gl/glfw3"
-	"github.com/hajimehoshi/ebiten/internal/graphics"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
-	"image"
 	"runtime"
 )
 
-var currentUI *ui
+var currentUI *UI
+
+func Current() *UI {
+	return currentUI
+}
 
 func init() {
 	runtime.LockOSThread()
@@ -42,28 +44,32 @@ func init() {
 		panic(err)
 	}
 
-	u := &ui{
+	u := &UI{
 		window: window,
 		funcs:  make(chan func()),
 	}
-	u.run()
-	u.use(func() {
+	go func() {
+		runtime.LockOSThread()
+		u.window.MakeContextCurrent()
 		u.glContext = opengl.NewContext()
 		glfw.SwapInterval(1)
-	})
+		for f := range u.funcs {
+			f()
+		}
+	}()
 	currentUI = u
 }
 
-type ui struct {
-	window          *glfw.Window
-	scale           int
-	glContext       *opengl.Context
-	graphicsContext *graphicsContext
-	input           input
-	funcs           chan func()
+type UI struct {
+	window    *glfw.Window
+	scale     int
+	realScale int
+	glContext *opengl.Context
+	input     input
+	funcs     chan func()
 }
 
-func startUI(width, height, scale int, title string) (*ui, error) {
+func New(width, height, scale int, title string) (*UI, error) {
 	monitor, err := glfw.GetPrimaryMonitor()
 	if err != nil {
 		return nil, err
@@ -103,101 +109,41 @@ func startUI(width, height, scale int, title string) (*ui, error) {
 
 	// For retina displays, recalculate the scale with the framebuffer size.
 	windowWidth, _ := window.GetFramebufferSize()
-	realScale := windowWidth / width
-	ui.use(func() {
-		ui.graphicsContext, err = newGraphicsContext(ui.glContext, width, height, realScale)
-	})
+	ui.realScale = windowWidth / width
+
 	return ui, err
 }
 
-func (u *ui) doEvents() {
-	glfw.PollEvents()
-	u.update()
+func (u *UI) RealScale() int {
+	return u.realScale
 }
 
-func (u *ui) terminate() {
+func (u *UI) DoEvents() {
+	glfw.PollEvents()
+	u.input.update(u.window, u.scale)
+}
+
+func (u *UI) Terminate() {
 	glfw.Terminate()
 }
 
-func (u *ui) isClosed() bool {
+func (u *UI) IsClosed() bool {
 	return u.window.ShouldClose()
 }
 
-func (u *ui) draw(f func(*Image) error) (err error) {
-	u.use(func() {
-		err = u.graphicsContext.preUpdate()
-	})
-	if err != nil {
-		return
-	}
-	err = f(&Image{ui: u, inner: u.graphicsContext.screen})
-	if err != nil {
-		return
-	}
-	u.use(func() {
-		err = u.graphicsContext.postUpdate()
-		if err != nil {
-			return
-		}
-		u.window.SwapBuffers()
-	})
-	return
+func (u *UI) SwapBuffers() {
+	u.window.SwapBuffers()
 }
 
-func (u *ui) newImageFromImage(img image.Image, filter Filter) (*Image, error) {
-	var innerImage *innerImage
-	var err error
-	u.use(func() {
-		var texture *graphics.Texture
-		texture, err = graphics.NewTextureFromImage(u.glContext, img, glFilter(u.glContext, filter))
-		if err != nil {
-			return
-		}
-		innerImage, err = newInnerImage(u.glContext, texture)
-	})
-	if err != nil {
-		return nil, err
-	}
-	return &Image{ui: u, inner: innerImage}, nil
+func (u *UI) Input() *input {
+	return &u.input
 }
 
-func (u *ui) newImage(width, height int, filter Filter) (*Image, error) {
-	var innerImage *innerImage
-	var err error
-	u.use(func() {
-		var texture *graphics.Texture
-		texture, err = graphics.NewTexture(u.glContext, width, height, glFilter(u.glContext, filter))
-		if err != nil {
-			return
-		}
-		innerImage, err = newInnerImage(u.glContext, texture)
-		innerImage.Clear(u.glContext)
-	})
-	if err != nil {
-		return nil, err
-	}
-	return &Image{ui: u, inner: innerImage}, nil
-}
-
-func (u *ui) run() {
-	go func() {
-		runtime.LockOSThread()
-		u.window.MakeContextCurrent()
-		for f := range u.funcs {
-			f()
-		}
-	}()
-}
-
-func (u *ui) use(f func()) {
+func (u *UI) Use(f func(*opengl.Context)) {
 	ch := make(chan struct{})
 	u.funcs <- func() {
 		defer close(ch)
-		f()
+		f(u.glContext)
 	}
 	<-ch
 }
-
-func (u *ui) update() {
-	u.input.update(u.window, u.scale)
-}
diff --git a/keys.go b/keys.go
index 96a738102..645fea22f 100644
--- a/keys.go
+++ b/keys.go
@@ -14,19 +14,25 @@
 
 package ebiten
 
+import (
+	"github.com/hajimehoshi/ebiten/internal/ui"
+)
+
 // A Key represents a keyboard key.
 type Key int
 
 // TODO: Add more keys.
 
+// TODO: Generate this automatically.
+
 // Keys
 const (
-	KeyUp Key = iota
-	KeyDown
-	KeyLeft
-	KeyRight
-	KeySpace
-	KeyMax
+	KeyUp    = Key(ui.KeyUp)
+	KeyDown  = Key(ui.KeyDown)
+	KeyLeft  = Key(ui.KeyLeft)
+	KeyRight = Key(ui.KeyRight)
+	KeySpace = Key(ui.KeySpace)
+	KeyMax   = Key(ui.KeyMax)
 )
 
 // A MouseButton represents a mouse button.
@@ -34,8 +40,8 @@ type MouseButton int
 
 // MouseButtons
 const (
-	MouseButtonLeft MouseButton = iota
-	MouseButtonRight
-	MouseButtonMiddle
-	MouseButtonMax
+	MouseButtonLeft   = MouseButton(ui.MouseButtonLeft)
+	MouseButtonRight  = MouseButton(ui.MouseButtonRight)
+	MouseButtonMiddle = MouseButton(ui.MouseButtonMiddle)
+	MouseButtonMax    = MouseButton(ui.MouseButtonMax)
 )
diff --git a/run.go b/run.go
index c3e20d2a1..063f75371 100644
--- a/run.go
+++ b/run.go
@@ -15,6 +15,8 @@
 package ebiten
 
 import (
+	"github.com/hajimehoshi/ebiten/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/ui"
 	"time"
 )
 
@@ -28,20 +30,44 @@ import (
 // but this is not strictly guaranteed.
 // If you need to care about time, you need to check current time every time f is called.
 func Run(f func(*Image) error, width, height, scale int, title string) error {
-	ui, err := startUI(width, height, scale, title)
+	ui, err := ui.New(width, height, scale, title)
+	if err != nil {
+		return err
+	}
+	defer ui.Terminate()
+
+	var graphicsContext *graphicsContext
+	ui.Use(func(c *opengl.Context) {
+		graphicsContext, err = newGraphicsContext(c, width, height, ui.RealScale())
+	})
 	if err != nil {
 		return err
 	}
-	defer ui.terminate()
 
 	for {
 		// To avoid busy loop when the window is inactive, wait 1/120 [sec] at least.
 		ch := time.After(1 * time.Second / 120)
-		ui.doEvents()
-		if ui.isClosed() {
+		ui.DoEvents()
+		if ui.IsClosed() {
 			return nil
 		}
-		if err := ui.draw(f); err != nil {
+		ui.Use(func(*opengl.Context) {
+			err = graphicsContext.preUpdate()
+		})
+		if err != nil {
+			return err
+		}
+		if err := f(&Image{ui: ui, inner: graphicsContext.screen}); err != nil {
+			return err
+		}
+		ui.Use(func(*opengl.Context) {
+			err = graphicsContext.postUpdate()
+			if err != nil {
+				return
+			}
+			ui.SwapBuffers()
+		})
+		if err != nil {
 			return err
 		}
 		<-ch