diff --git a/internal/ui/input_glfw.go b/internal/ui/input_glfw.go
index 5c6f5422f..e9ce2d918 100644
--- a/internal/ui/input_glfw.go
+++ b/internal/ui/input_glfw.go
@@ -33,14 +33,6 @@ func CursorPosition() (x, y int) {
 	return current.input.cursorPosition()
 }
 
-var glfwKeyCodeToKey = map[glfw.Key]Key{
-	glfw.KeySpace: KeySpace,
-	glfw.KeyLeft:  KeyLeft,
-	glfw.KeyRight: KeyRight,
-	glfw.KeyUp:    KeyUp,
-	glfw.KeyDown:  KeyDown,
-}
-
 func (i *input) update(window *glfw.Window, scale int) {
 	for g, u := range glfwKeyCodeToKey {
 		i.keyPressed[u] = window.GetKey(g) == glfw.Press
diff --git a/internal/ui/input_js.go b/internal/ui/input_js.go
index aaccef39a..b8c378fc5 100644
--- a/internal/ui/input_js.go
+++ b/internal/ui/input_js.go
@@ -16,14 +16,6 @@
 
 package ui
 
-var keyCodeToKey = map[int]Key{
-	32: KeySpace,
-	37: KeyLeft,
-	39: KeyRight,
-	38: KeyUp,
-	40: KeyDown,
-}
-
 var currentInput input
 
 func IsKeyPressed(key Key) bool {
diff --git a/internal/ui/keys_glfw.go b/internal/ui/keys_glfw.go
new file mode 100644
index 000000000..2df7ce4b1
--- /dev/null
+++ b/internal/ui/keys_glfw.go
@@ -0,0 +1,29 @@
+// 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.
+// 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 ui
+
+import (
+	glfw "github.com/go-gl/glfw3"
+)
+
+var glfwKeyCodeToKey = map[glfw.Key]Key{
+	glfw.KeySpace: KeySpace,
+	glfw.KeyLeft:  KeyLeft,
+	glfw.KeyRight: KeyRight,
+	glfw.KeyUp:    KeyUp,
+	glfw.KeyDown:  KeyDown,
+}
diff --git a/internal/ui/keys_js.go b/internal/ui/keys_js.go
new file mode 100644
index 000000000..29ebf9b27
--- /dev/null
+++ b/internal/ui/keys_js.go
@@ -0,0 +1,25 @@
+// 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.
+// 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 ui
+
+var keyCodeToKey = map[int]Key{
+	32: KeySpace,
+	37: KeyLeft,
+	39: KeyRight,
+	38: KeyUp,
+	40: KeyDown,
+}
diff --git a/keys.go b/keys.go
index 645fea22f..c77eeb248 100644
--- a/keys.go
+++ b/keys.go
@@ -21,10 +21,6 @@ import (
 // A Key represents a keyboard key.
 type Key int
 
-// TODO: Add more keys.
-
-// TODO: Generate this automatically.
-
 // Keys
 const (
 	KeyUp    = Key(ui.KeyUp)