diff --git a/internal/graphics/internal/shader/program.go b/internal/graphics/internal/shader/program.go
index cd394fa0a..1980799ba 100644
--- a/internal/graphics/internal/shader/program.go
+++ b/internal/graphics/internal/shader/program.go
@@ -47,8 +47,8 @@ func initialize(c *opengl.Context) error {
 	}
 
 	const stride = 4 * 4
-	s := float32Size * stride * size
-	c.NewBuffer(c.ArrayBuffer, s, nil, c.DynamicDraw)
+	v := make([]float32, stride*size)
+	c.NewBuffer(c.ArrayBuffer, v, c.DynamicDraw)
 
 	indices := make([]uint16, 6*size)
 	for i := uint16(0); i < size; i++ {
@@ -59,7 +59,7 @@ func initialize(c *opengl.Context) error {
 		indices[6*i+4] = 4*i + 2
 		indices[6*i+5] = 4*i + 3
 	}
-	c.NewBuffer(c.ElementArrayBuffer, uint16Size*len(indices), indices, c.StaticDraw)
+	c.NewBuffer(c.ElementArrayBuffer, indices, c.StaticDraw)
 
 	return nil
 }
diff --git a/internal/opengl/context.go b/internal/opengl/context.go
index e10eadef3..920a74e2c 100644
--- a/internal/opengl/context.go
+++ b/internal/opengl/context.go
@@ -22,21 +22,12 @@ import (
 	"github.com/go-gl/gl"
 )
 
-type Texture gl.Texture
-type Framebuffer gl.Framebuffer
-type Shader gl.Shader
-type Program gl.Program
+type Texture int
+type Framebuffer int
+type Shader int
+type Program int
 
-type Context struct {
-	Nearest            FilterType
-	Linear             FilterType
-	VertexShader       ShaderType
-	FragmentShader     ShaderType
-	ArrayBuffer        BufferType
-	ElementArrayBuffer BufferType
-	DynamicDraw        BufferUsageType
-	StaticDraw         BufferUsageType
-}
+type context struct{}
 
 func NewContext() *Context {
 	c := &Context{
@@ -202,9 +193,18 @@ func (c *Context) DisableVertexAttribArray(p Program, location string) {
 	gl.Program(p).GetAttribLocation(location).DisableArray()
 }
 
-func (c *Context) NewBuffer(bufferType BufferType, size int, ptr interface{}, bufferUsageType BufferUsageType) {
+func (c *Context) NewBuffer(bufferType BufferType, v interface{}, bufferUsageType BufferUsageType) {
 	gl.GenBuffer().Bind(gl.GLenum(bufferType))
-	gl.BufferData(gl.GLenum(bufferType), size, ptr, gl.GLenum(bufferUsageType))
+	size := 0
+	switch v := v.(type) {
+	case []uint16:
+		size = 2 * len(v)
+	case []float32:
+		size = 4 * len(v)
+	default:
+		panic("not reach")
+	}
+	gl.BufferData(gl.GLenum(bufferType), size, v, gl.GLenum(bufferUsageType))
 }
 
 func (c *Context) BufferSubData(bufferType BufferType, data []float32) {
diff --git a/internal/opengl/context_js.go b/internal/opengl/context_js.go
new file mode 100644
index 000000000..770f94d84
--- /dev/null
+++ b/internal/opengl/context_js.go
@@ -0,0 +1,240 @@
+// Copyright 2014 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build js
+
+package opengl
+
+import (
+	"errors"
+	"fmt"
+	"github.com/gopherjs/gopherjs/js"
+	"github.com/gopherjs/webgl"
+)
+
+type Texture js.Object
+type Framebuffer js.Object
+type Shader js.Object
+type Program js.Object
+
+type context struct {
+	gl *webgl.Context
+}
+
+func NewContext(gl *webgl.Context) *Context {
+	c := &Context{
+		Nearest:            FilterType(gl.NEAREST),
+		Linear:             FilterType(gl.LINEAR),
+		VertexShader:       ShaderType(gl.VERTEX_SHADER),
+		FragmentShader:     ShaderType(gl.FRAGMENT_SHADER),
+		ArrayBuffer:        BufferType(gl.ARRAY_BUFFER),
+		ElementArrayBuffer: BufferType(gl.ELEMENT_ARRAY_BUFFER),
+		DynamicDraw:        BufferUsageType(gl.DYNAMIC_DRAW),
+		StaticDraw:         BufferUsageType(gl.STATIC_DRAW),
+	}
+	c.init()
+	return c
+}
+
+func (c *Context) init() {
+	gl := c.gl
+	gl.Enable(gl.TEXTURE_2D)
+	// Textures' pixel formats are alpha premultiplied.
+	gl.Enable(gl.BLEND)
+	gl.BlendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA)
+}
+
+func (c *Context) NewTexture(width, height int, pixels []uint8, filter FilterType) (Texture, error) {
+	gl := c.gl
+	t := gl.CreateTexture()
+	if t.IsNull() {
+		return nil, errors.New("glGenTexture failed")
+	}
+	gl.PixelStorei(gl.UNPACK_ALIGNMENT, 4)
+	gl.BindTexture(gl.TEXTURE_2D, t)
+	defer gl.BindTexture(gl.TEXTURE_2D, nil)
+
+	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, int(filter))
+	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, int(filter))
+
+	// void texImage2D(GLenum target, GLint level, GLenum internalformat,
+	//     GLsizei width, GLsizei height, GLint border, GLenum format,
+	//     GLenum type, ArrayBufferView? pixels);
+	gl.Call("texImage2D", gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, pixels)
+
+	return Texture(t), nil
+}
+
+func (c *Context) TexturePixels(t Texture, width, height int) ([]uint8, error) {
+	gl := c.gl
+	// TODO: Use glGetTexLevelParameteri and GL_TEXTURE_WIDTH?
+	pixels := js.Global.Get("Uint8Array").New(4 * width * height)
+	gl.BindTexture(gl.TEXTURE_2D, t)
+	gl.ReadPixels(0, 0, width, height, gl.RGBA, gl.UNSIGNED_BYTE, pixels)
+	if e := gl.GetError(); e != gl.NO_ERROR {
+		// TODO: Use glu.ErrorString
+		return nil, errors.New(fmt.Sprintf("gl error: %d", e))
+	}
+	return pixels.Interface().([]uint8), nil
+}
+
+func (c *Context) BindTexture(t Texture) {
+	gl := c.gl
+	gl.BindTexture(gl.TEXTURE_2D, t)
+}
+
+func (c *Context) DeleteTexture(t Texture) {
+	gl := c.gl
+	gl.DeleteTexture(t)
+}
+
+func (c *Context) NewFramebuffer(texture Texture) (Framebuffer, error) {
+	gl := c.gl
+	f := gl.CreateFramebuffer()
+	gl.BindFramebuffer(gl.FRAMEBUFFER, f)
+
+	gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0)
+	if gl.CheckFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE {
+		return nil, errors.New("creating framebuffer failed")
+	}
+
+	return Framebuffer(f), nil
+}
+
+func (c *Context) SetViewport(f Framebuffer, width, height int) error {
+	gl := c.gl
+	gl.Flush()
+	gl.BindFramebuffer(gl.FRAMEBUFFER, f)
+	err := gl.CheckFramebufferStatus(gl.FRAMEBUFFER)
+	if err != gl.FRAMEBUFFER_COMPLETE {
+		if gl.GetError() != 0 {
+			return errors.New(fmt.Sprintf("glBindFramebuffer failed: %d", gl.GetError()))
+		}
+		return errors.New("glBindFramebuffer failed: the context is different?")
+	}
+	gl.Viewport(0, 0, width, height)
+	return nil
+}
+
+func (c *Context) FillFramebuffer(f Framebuffer, r, g, b, a float64) error {
+	gl := c.gl
+	gl.ClearColor(float32(r), float32(g), float32(b), float32(a))
+	gl.Clear(gl.COLOR_BUFFER_BIT)
+	return nil
+}
+
+func (c *Context) DeleteFramebuffer(f Framebuffer) {
+	gl := c.gl
+	gl.DeleteFramebuffer(f)
+}
+
+func (c *Context) NewShader(shaderType ShaderType, source string) (Shader, error) {
+	gl := c.gl
+	s := gl.CreateShader(int(shaderType))
+	if s.IsNull() {
+		println(gl.GetError())
+		return nil, errors.New("glCreateShader failed")
+	}
+
+	gl.ShaderSource(s, source)
+	gl.CompileShader(s)
+
+	if !gl.GetShaderParameterb(s, gl.COMPILE_STATUS) {
+		log := gl.GetShaderInfoLog(s)
+		return nil, errors.New(fmt.Sprintf("shader compile failed: %s", log))
+	}
+	return Shader(s), nil
+}
+
+func (c *Context) DeleteShader(s Shader) {
+	gl := c.gl
+	gl.DeleteShader(s)
+}
+
+func (c *Context) NewProgram(shaders []Shader) (Program, error) {
+	gl := c.gl
+	p := gl.CreateProgram()
+	if p.IsNull() {
+		return nil, errors.New("glCreateProgram failed")
+	}
+
+	for _, shader := range shaders {
+		gl.AttachShader(p, shader)
+	}
+	gl.LinkProgram(p)
+	if !gl.GetProgramParameterb(p, gl.LINK_STATUS) {
+		return nil, errors.New("program error")
+	}
+	return Program(p), nil
+}
+
+func (c *Context) UseProgram(p Program) {
+	gl := c.gl
+	gl.UseProgram(p)
+}
+
+func (c *Context) Uniform(p Program, location string, v interface{}) {
+	gl := c.gl
+	l := gl.GetUniformLocation(p, location)
+	switch v := v.(type) {
+	case int:
+		gl.Uniform1i(l, v)
+	case [4]float32:
+		gl.Call("uniform4fv", l, v[:])
+	case [16]float32:
+		gl.UniformMatrix4fv(l, false, v[:])
+	}
+}
+
+func (c *Context) VertexAttribPointer(p Program, location string, stride int, v uintptr) {
+	gl := c.gl
+	l := gl.GetAttribLocation(p, location)
+	gl.VertexAttribPointer(l, 2, gl.FLOAT, false, stride, int(v))
+}
+
+func (c *Context) EnableVertexAttribArray(p Program, location string) {
+	gl := c.gl
+	l := gl.GetAttribLocation(p, location)
+	gl.EnableVertexAttribArray(l)
+}
+
+func (c *Context) DisableVertexAttribArray(p Program, location string) {
+	gl := c.gl
+	l := gl.GetAttribLocation(p, location)
+	gl.DisableVertexAttribArray(l)
+}
+
+func (c *Context) NewBuffer(bufferType BufferType, v interface{}, bufferUsageType BufferUsageType) {
+	gl := c.gl
+	b := gl.CreateBuffer()
+	gl.BindBuffer(int(bufferType), b)
+	// TODO: Can we assign integer to gl.bufferData?
+	gl.BufferData(int(bufferType), v, int(bufferUsageType))
+}
+
+func (c *Context) BufferSubData(bufferType BufferType, data []float32) {
+	gl := c.gl
+	const float32Size = 4
+	gl.BufferSubData(int(bufferType), 0, data)
+}
+
+func (c *Context) DrawElements(len int) {
+	gl := c.gl
+	gl.DrawElements(gl.TRIANGLES, len, gl.UNSIGNED_SHORT, 0)
+}
+
+func (c *Context) Flush() {
+	gl := c.gl
+	gl.Flush()
+}
diff --git a/internal/opengl/types.go b/internal/opengl/types.go
index 901a93bcb..a93e76648 100644
--- a/internal/opengl/types.go
+++ b/internal/opengl/types.go
@@ -18,3 +18,15 @@ type FilterType int
 type ShaderType int
 type BufferType int
 type BufferUsageType int
+
+type Context struct {
+	Nearest            FilterType
+	Linear             FilterType
+	VertexShader       ShaderType
+	FragmentShader     ShaderType
+	ArrayBuffer        BufferType
+	ElementArrayBuffer BufferType
+	DynamicDraw        BufferUsageType
+	StaticDraw         BufferUsageType
+	*context
+}