diff --git a/ebiten.go b/ebiten.go
index 3857bde2e..e9e3e64ef 100644
--- a/ebiten.go
+++ b/ebiten.go
@@ -1,9 +1,9 @@
 package ebiten
 
 import (
-	"time"
 	"github.com/hajimehoshi/go-ebiten/graphics"
 	"github.com/hajimehoshi/go-ebiten/graphics/opengl"
+	"time"
 )
 
 type Game interface {
@@ -26,7 +26,7 @@ func OpenGLRun(game Game, ui UI) {
 		func(g graphics.GraphicsContext, offscreen graphics.TextureID) {
 			ticket := <-ch
 			game.Draw(g, offscreen)
-			ch<- ticket
+			ch <- ticket
 		})
 
 	go func() {
@@ -36,11 +36,11 @@ func OpenGLRun(game Game, ui UI) {
 			<-tick
 			ticket := <-ch
 			game.Update()
-			ch<- ticket
+			ch <- ticket
 		}
 	}()
 
 	game.Init(device.TextureFactory())
-	ch<- true
+	ch <- true
 	ui.Run(device)
 }
diff --git a/examples/glut/main.go b/examples/glut/main.go
index 9e400cf31..3c91f8981 100644
--- a/examples/glut/main.go
+++ b/examples/glut/main.go
@@ -15,21 +15,21 @@ package main
 //
 import "C"
 import (
+	"github.com/hajimehoshi/go-ebiten"
+	"github.com/hajimehoshi/go-ebiten/graphics"
 	"image"
 	"image/color"
 	_ "image/png"
 	"os"
 	"runtime"
 	"unsafe"
-	"github.com/hajimehoshi/go-ebiten"
-	"github.com/hajimehoshi/go-ebiten/graphics"
 )
 
-type GlutUI struct{
-	screenWidth int
+type GlutUI struct {
+	screenWidth  int
 	screenHeight int
-	screenScale int
-	device graphics.Device
+	screenScale  int
+	device       graphics.Device
 }
 
 var currentUI *GlutUI
@@ -57,15 +57,15 @@ func (ui *GlutUI) Init() {
 	}()
 	cargc := C.int(len(cargs))
 
-	ui.screenWidth  = 256
+	ui.screenWidth = 256
 	ui.screenHeight = 240
-	ui.screenScale  = 2
+	ui.screenScale = 2
 
 	C.glutInit(&cargc, &cargs[0])
-	C.glutInitDisplayMode(C.GLUT_RGBA);
+	C.glutInitDisplayMode(C.GLUT_RGBA)
 	C.glutInitWindowSize(
-		C.int(ui.screenWidth  * ui.screenScale),
-		C.int(ui.screenHeight * ui.screenScale))
+		C.int(ui.screenWidth*ui.screenScale),
+		C.int(ui.screenHeight*ui.screenScale))
 
 	title := C.CString("Ebiten Demo")
 	defer C.free(unsafe.Pointer(title))
@@ -93,7 +93,7 @@ func (ui *GlutUI) Run(device graphics.Device) {
 
 type DemoGame struct {
 	ebitenTexture graphics.Texture
-	x int
+	x             int
 }
 
 func (game *DemoGame) Init(tf graphics.TextureFactory) {
@@ -102,7 +102,7 @@ func (game *DemoGame) Init(tf graphics.TextureFactory) {
 		panic(err)
 	}
 	defer file.Close()
-	
+
 	img, _, err := image.Decode(file)
 	if err != nil {
 		panic(err)
diff --git a/graphics/affine_matrix_test.go b/graphics/affine_matrix_test.go
index 39a727f30..82bb1edb8 100644
--- a/graphics/affine_matrix_test.go
+++ b/graphics/affine_matrix_test.go
@@ -1,8 +1,8 @@
 package graphics_test
 
 import (
-	"testing"
 	. "."
+	"testing"
 )
 
 func setElements(matrix *AffineMatrix, elements [][]float64) {
diff --git a/graphics/geometry_matrix_test.go b/graphics/geometry_matrix_test.go
index 45cd7690d..8f737e10f 100644
--- a/graphics/geometry_matrix_test.go
+++ b/graphics/geometry_matrix_test.go
@@ -1,8 +1,8 @@
 package graphics_test
 
 import (
-	"testing"
 	. "."
+	"testing"
 )
 
 func TestGeometryMatrixElements(t *testing.T) {
diff --git a/graphics/graphics.go b/graphics/graphics.go
index 10dc5ff2b..b0be06b32 100644
--- a/graphics/graphics.go
+++ b/graphics/graphics.go
@@ -25,8 +25,8 @@ type TextureFactory interface {
 }
 
 type Texture struct {
-	ID TextureID
-	Width int
+	ID     TextureID
+	Width  int
 	Height int
 }
 
diff --git a/graphics/opengl/device.go b/graphics/opengl/device.go
index fea10e6b9..e490ad8ff 100644
--- a/graphics/opengl/device.go
+++ b/graphics/opengl/device.go
@@ -10,22 +10,22 @@ import (
 )
 
 type Device struct {
-	screenWidth int
-	screenHeight int
-	screenScale int
-	graphicsContext *GraphicsContext
+	screenWidth      int
+	screenHeight     int
+	screenScale      int
+	graphicsContext  *GraphicsContext
 	offscreenTexture graphics.Texture
-	drawFunc func(graphics.GraphicsContext, graphics.TextureID)
+	drawFunc         func(graphics.GraphicsContext, graphics.TextureID)
 }
 
 func NewDevice(screenWidth, screenHeight, screenScale int,
 	drawFunc func(graphics.GraphicsContext, graphics.TextureID)) *Device {
 	device := &Device{
-		screenWidth: screenWidth,
-		screenHeight: screenHeight,
-		screenScale: screenScale,
+		screenWidth:     screenWidth,
+		screenHeight:    screenHeight,
+		screenScale:     screenScale,
 		graphicsContext: newGraphicsContext(screenWidth, screenHeight, screenScale),
-		drawFunc: drawFunc,
+		drawFunc:        drawFunc,
 	}
 	device.offscreenTexture =
 		device.graphicsContext.NewTexture(screenWidth, screenHeight)
@@ -41,7 +41,7 @@ func (device *Device) Update() {
 	g.Clear()
 	device.drawFunc(g, device.offscreenTexture.ID)
 	g.flush()
-	
+
 	C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MIN_FILTER, C.GL_LINEAR)
 	C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MAG_FILTER, C.GL_LINEAR)
 	g.resetOffscreen()
diff --git a/graphics/opengl/graphics_context.go b/graphics/opengl/graphics_context.go
index a5200b6e5..acf770cda 100644
--- a/graphics/opengl/graphics_context.go
+++ b/graphics/opengl/graphics_context.go
@@ -7,32 +7,32 @@ package opengl
 import "C"
 import (
 	"fmt"
+	"github.com/hajimehoshi/go-ebiten/graphics"
 	"image"
 	"image/color"
 	"unsafe"
-	"github.com/hajimehoshi/go-ebiten/graphics"
 )
 
 type GraphicsContext struct {
-	screenWidth int
-	screenHeight int
-	screenScale int
-	textures map[graphics.TextureID]*Texture
-	projectionMatrix [16]float32
+	screenWidth          int
+	screenHeight         int
+	screenScale          int
+	textures             map[graphics.TextureID]*Texture
+	projectionMatrix     [16]float32
 	currentShaderProgram C.GLuint
-	mainFramebuffer C.GLuint
-	framebuffers map[C.GLuint]C.GLuint
+	mainFramebuffer      C.GLuint
+	framebuffers         map[C.GLuint]C.GLuint
 }
 
 // This method should be called on the UI thread.
 func newGraphicsContext(screenWidth, screenHeight, screenScale int) *GraphicsContext {
 	context := &GraphicsContext{
-		screenWidth: screenWidth,
-		screenHeight: screenHeight,
-		screenScale: screenScale,
-		textures: map[graphics.TextureID]*Texture{},
+		screenWidth:     screenWidth,
+		screenHeight:    screenHeight,
+		screenScale:     screenScale,
+		textures:        map[graphics.TextureID]*Texture{},
 		mainFramebuffer: 0,
-		framebuffers: map[C.GLuint]C.GLuint{},
+		framebuffers:    map[C.GLuint]C.GLuint{},
 	}
 	// main framebuffer should be created sooner than any other framebuffers!
 	mainFramebuffer := C.GLint(0)
@@ -53,10 +53,10 @@ func (context *GraphicsContext) Fill(clr color.Color) {
 	r, g, b, a := clr.RGBA()
 	max := 65535.0
 	C.glClearColor(
-		C.GLclampf(float64(r) / max),
-		C.GLclampf(float64(g) / max),
-		C.GLclampf(float64(b) / max),
-		C.GLclampf(float64(a) / max))
+		C.GLclampf(float64(r)/max),
+		C.GLclampf(float64(g)/max),
+		C.GLclampf(float64(b)/max),
+		C.GLclampf(float64(a)/max))
 	C.glClear(C.GL_COLOR_BUFFER_BIT)
 }
 
@@ -69,7 +69,7 @@ func (context *GraphicsContext) DrawTexture(
 	srcX, srcY, srcWidth, srcHeight int,
 	geometryMatrix *graphics.GeometryMatrix, colorMatrix *graphics.ColorMatrix) {
 	geometryMatrix = geometryMatrix.Clone()
-	colorMatrix    = colorMatrix.Clone()
+	colorMatrix = colorMatrix.Clone()
 
 	texture := context.textures[textureID]
 
@@ -87,10 +87,10 @@ func (context *GraphicsContext) DrawTexture(
 		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,
@@ -138,8 +138,7 @@ func (context *GraphicsContext) setOffscreenFramebuffer(framebuffer C.GLuint,
 	C.glFlush()
 
 	C.glBindFramebuffer(C.GL_FRAMEBUFFER, framebuffer)
-	if err := C.glCheckFramebufferStatus(C.GL_FRAMEBUFFER);
-	err != C.GL_FRAMEBUFFER_COMPLETE {
+	if err := C.glCheckFramebufferStatus(C.GL_FRAMEBUFFER); err != C.GL_FRAMEBUFFER_COMPLETE {
 		panic(fmt.Sprintf("glBindFramebuffer failed: %d", err))
 	}
 	C.glEnable(C.GL_BLEND)
@@ -147,15 +146,15 @@ func (context *GraphicsContext) setOffscreenFramebuffer(framebuffer C.GLuint,
 
 	width, height, tx, ty := 0, 0, 0, 0
 	if framebuffer != context.mainFramebuffer {
-		width  = textureWidth
+		width = textureWidth
 		height = textureHeight
-		tx     = -1
-		ty     = -1
+		tx = -1
+		ty = -1
 	} else {
-		width  = context.screenWidth * context.screenScale
+		width = context.screenWidth * context.screenScale
 		height = -1 * context.screenHeight * context.screenScale
-		tx     = -1
-		ty     = 1
+		tx = -1
+		ty = 1
 	}
 	C.glViewport(0, 0, C.GLsizei(abs(width)), C.GLsizei(abs(height)))
 	e11 := float32(2.0) / float32(width)
@@ -163,9 +162,9 @@ func (context *GraphicsContext) setOffscreenFramebuffer(framebuffer C.GLuint,
 	e41 := float32(tx)
 	e42 := float32(ty)
 	context.projectionMatrix = [...]float32{
-		e11, 0,   0, 0,
-		0,   e22, 0, 0,
-		0,   0,   1, 0,
+		e11, 0, 0, 0,
+		0, e22, 0, 0,
+		0, 0, 1, 0,
 		e41, e42, 0, 1,
 	}
 }
@@ -196,16 +195,16 @@ func (context *GraphicsContext) setShaderProgram(
 		1, C.GL_FALSE,
 		(*C.GLfloat)(&context.projectionMatrix[0]))
 
-	a  := float32(geometryMatrix.A())
-	b  := float32(geometryMatrix.B())
-	c  := float32(geometryMatrix.C())
-	d  := float32(geometryMatrix.D())
+	a := float32(geometryMatrix.A())
+	b := float32(geometryMatrix.B())
+	c := float32(geometryMatrix.C())
+	d := float32(geometryMatrix.D())
 	tx := float32(geometryMatrix.Tx())
 	ty := float32(geometryMatrix.Ty())
 	glModelviewMatrix := [...]float32{
-		a,  c,  0, 0,
-		b,  d,  0, 0,
-		0,  0,  1, 0,
+		a, c, 0, 0,
+		b, d, 0, 0,
+		0, 0, 1, 0,
 		tx, ty, 0, 1,
 	}
 	C.glUniformMatrix4fv(getUniformLocation(program, "modelview_matrix"),
@@ -241,7 +240,7 @@ func (context *GraphicsContext) setShaderProgram(
 		1, (*C.GLfloat)(&glColorMatrixTranslation[0]))
 }
 
-func (context *GraphicsContext) getFramebuffer(textureID C.GLuint) C.GLuint{
+func (context *GraphicsContext) getFramebuffer(textureID C.GLuint) C.GLuint {
 	framebuffer, ok := context.framebuffers[textureID]
 	if ok {
 		return framebuffer
diff --git a/graphics/opengl/shader.go b/graphics/opengl/shader.go
index 23912d1eb..323ec3c5b 100644
--- a/graphics/opengl/shader.go
+++ b/graphics/opengl/shader.go
@@ -10,14 +10,14 @@ import (
 )
 
 type shader struct {
-	id C.GLuint
-	name string
+	id     C.GLuint
+	name   string
 	source string
 }
 
 var (
 	vertexShader = &shader{
-		id: 0,
+		id:   0,
 		name: "vertex_shader",
 		source: `
 attribute /*highp*/ vec2 vertex;
@@ -33,7 +33,7 @@ void main(void) {
 `,
 	}
 	fragmentShader = &shader{
-		id: 0,
+		id:   0,
 		name: "fragment_shader",
 		source: `
 uniform /*lowp*/ sampler2D texture;
@@ -45,7 +45,7 @@ void main(void) {
 `,
 	}
 	colorMatrixShader = &shader{
-		id: 0,
+		id:   0,
 		name: "color_matrix_shader",
 		source: `
 uniform /*highp*/ sampler2D texture;
@@ -62,7 +62,7 @@ void main(void) {
 )
 
 var (
-	regularShaderProgram = C.GLuint(0)
+	regularShaderProgram     = C.GLuint(0)
 	colorMatrixShaderProgram = C.GLuint(0)
 )
 
diff --git a/graphics/opengl/texture.go b/graphics/opengl/texture.go
index ccc42bea9..2d6045ae2 100644
--- a/graphics/opengl/texture.go
+++ b/graphics/opengl/texture.go
@@ -21,15 +21,15 @@ func Clp2(x uint64) uint64 {
 }
 
 type Texture struct {
-	id C.GLuint
-	width int
-	height int
-	textureWidth int
+	id            C.GLuint
+	width         int
+	height        int
+	textureWidth  int
 	textureHeight int
 }
 
 func createTexture(width, height int, pixels []uint8) *Texture {
-	textureWidth  := int(Clp2(uint64(width)))
+	textureWidth := int(Clp2(uint64(width)))
 	textureHeight := int(Clp2(uint64(height)))
 	if pixels != nil {
 		if width != textureWidth {
@@ -40,10 +40,10 @@ func createTexture(width, height int, pixels []uint8) *Texture {
 		}
 	}
 	texture := &Texture{
-		id: 0,
-		width: width,
-		height: height,
-		textureWidth: textureWidth,
+		id:            0,
+		width:         width,
+		height:        height,
+		textureWidth:  textureWidth,
 		textureHeight: textureHeight,
 	}
 
@@ -54,7 +54,7 @@ func createTexture(width, height int, pixels []uint8) *Texture {
 	}
 	C.glPixelStorei(C.GL_UNPACK_ALIGNMENT, 4)
 	C.glBindTexture(C.GL_TEXTURE_2D, C.GLuint(textureID))
-	
+
 	ptr := unsafe.Pointer(nil)
 	if pixels != nil {
 		ptr = unsafe.Pointer(&pixels[0])
diff --git a/graphics/opengl/texture_test.go b/graphics/opengl/texture_test.go
index 13b64a156..a2f0e6629 100644
--- a/graphics/opengl/texture_test.go
+++ b/graphics/opengl/texture_test.go
@@ -1,14 +1,14 @@
 package opengl_test
 
 import (
-	"testing"
 	. "."
+	"testing"
 )
 
 func TestClp2(t *testing.T) {
 	testCases := []struct {
 		expected uint64
-		arg uint64
+		arg      uint64
 	}{
 		{256, 255},
 		{256, 256},
@@ -22,6 +22,6 @@ func TestClp2(t *testing.T) {
 			t.Errorf("Clp(%d) = %d, wanted %d",
 				testCase.arg, got, wanted)
 		}
-		
+
 	}
 }