diff --git a/internal/driver/ui.go b/internal/driver/ui.go
deleted file mode 100644
index 5f8625e88..000000000
--- a/internal/driver/ui.go
+++ /dev/null
@@ -1,52 +0,0 @@
-// Copyright 2019 The Ebiten Authors
-//
-// 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.
-
-package driver
-
-import (
-	"image"
-)
-
-type Window interface {
-	IsDecorated() bool
-	SetDecorated(decorated bool)
-
-	IsResizable() bool
-	SetResizable(resizable bool)
-
-	Position() (int, int)
-	SetPosition(x, y int)
-
-	Size() (int, int)
-	SetSize(width, height int)
-	SizeLimits() (minw, minh, maxw, maxh int)
-	SetSizeLimits(minw, minh, maxw, maxh int)
-
-	IsFloating() bool
-	SetFloating(floating bool)
-
-	Maximize()
-	IsMaximized() bool
-
-	Minimize()
-	IsMinimized() bool
-
-	SetIcon(iconImages []image.Image)
-	SetTitle(title string)
-	Restore()
-
-	IsBeingClosed() bool
-	SetClosingHandled(handled bool)
-	IsClosingHandled() bool
-}
diff --git a/internal/ui/ui_cbackend.go b/internal/ui/ui_cbackend.go
index 0e938b3ec..55e6f5af1 100644
--- a/internal/ui/ui_cbackend.go
+++ b/internal/ui/ui_cbackend.go
@@ -22,7 +22,6 @@ import (
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/cbackend"
-	"github.com/hajimehoshi/ebiten/v2/internal/driver"
 )
 
 const deviceScaleFactor = 1
@@ -132,6 +131,6 @@ func (*UserInterface) Input() *Input {
 	return &theUserInterface.input
 }
 
-func (*UserInterface) Window() driver.Window {
-	return nil
+func (*UserInterface) Window() *Window {
+	return &Window{}
 }
diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index 4d44d0762..3b274f809 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -27,7 +27,6 @@ import (
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/devicescale"
-	"github.com/hajimehoshi/ebiten/v2/internal/driver"
 	"github.com/hajimehoshi/ebiten/v2/internal/glfw"
 	"github.com/hajimehoshi/ebiten/v2/internal/hooks"
 	"github.com/hajimehoshi/ebiten/v2/internal/thread"
@@ -102,7 +101,7 @@ type UserInterface struct {
 	fpsModeInited bool
 
 	input   Input
-	iwindow window
+	iwindow Window
 
 	sizeCallback                   glfw.SizeCallback
 	closeCallback                  glfw.CloseCallback
@@ -1435,7 +1434,7 @@ func (u *UserInterface) Input() *Input {
 	return &u.input
 }
 
-func (u *UserInterface) Window() driver.Window {
+func (u *UserInterface) Window() *Window {
 	return &u.iwindow
 }
 
diff --git a/internal/ui/ui_js.go b/internal/ui/ui_js.go
index 3098904ae..ca03d9e36 100644
--- a/internal/ui/ui_js.go
+++ b/internal/ui/ui_js.go
@@ -19,7 +19,6 @@ import (
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/devicescale"
-	"github.com/hajimehoshi/ebiten/v2/internal/driver"
 	"github.com/hajimehoshi/ebiten/v2/internal/gamepad"
 	"github.com/hajimehoshi/ebiten/v2/internal/hooks"
 )
@@ -665,6 +664,6 @@ func (u *UserInterface) Input() *Input {
 	return &u.input
 }
 
-func (u *UserInterface) Window() driver.Window {
-	return nil
+func (u *UserInterface) Window() *Window {
+	return &Window{}
 }
diff --git a/internal/ui/ui_mobile.go b/internal/ui/ui_mobile.go
index 629778138..77af63119 100644
--- a/internal/ui/ui_mobile.go
+++ b/internal/ui/ui_mobile.go
@@ -34,7 +34,6 @@ import (
 	"golang.org/x/mobile/gl"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/devicescale"
-	"github.com/hajimehoshi/ebiten/v2/internal/driver"
 	"github.com/hajimehoshi/ebiten/v2/internal/gamepad"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
@@ -450,8 +449,8 @@ func (u *UserInterface) Input() *Input {
 	return &u.input
 }
 
-func (u *UserInterface) Window() driver.Window {
-	return nil
+func (u *UserInterface) Window() *Window {
+	return &Window{}
 }
 
 type Touch struct {
diff --git a/internal/ui/window_glfw.go b/internal/ui/window_glfw.go
index a73335bce..a84676356 100644
--- a/internal/ui/window_glfw.go
+++ b/internal/ui/window_glfw.go
@@ -23,11 +23,11 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/glfw"
 )
 
-type window struct {
+type Window struct {
 	ui *UserInterface
 }
 
-func (w *window) IsDecorated() bool {
+func (w *Window) IsDecorated() bool {
 	if !w.ui.isRunning() {
 		return w.ui.isInitWindowDecorated()
 	}
@@ -38,7 +38,7 @@ func (w *window) IsDecorated() bool {
 	return v
 }
 
-func (w *window) SetDecorated(decorated bool) {
+func (w *Window) SetDecorated(decorated bool) {
 	if !w.ui.isRunning() {
 		w.ui.setInitWindowDecorated(decorated)
 		return
@@ -53,7 +53,7 @@ func (w *window) SetDecorated(decorated bool) {
 	})
 }
 
-func (w *window) IsResizable() bool {
+func (w *Window) IsResizable() bool {
 	if !w.ui.isRunning() {
 		return w.ui.isInitWindowResizable()
 	}
@@ -64,7 +64,7 @@ func (w *window) IsResizable() bool {
 	return v
 }
 
-func (w *window) SetResizable(resizable bool) {
+func (w *Window) SetResizable(resizable bool) {
 	if !w.ui.isRunning() {
 		w.ui.setInitWindowResizable(resizable)
 		return
@@ -77,7 +77,7 @@ func (w *window) SetResizable(resizable bool) {
 	})
 }
 
-func (w *window) IsFloating() bool {
+func (w *Window) IsFloating() bool {
 	if !w.ui.isRunning() {
 		return w.ui.isInitWindowFloating()
 	}
@@ -88,7 +88,7 @@ func (w *window) IsFloating() bool {
 	return v
 }
 
-func (w *window) SetFloating(floating bool) {
+func (w *Window) SetFloating(floating bool) {
 	if !w.ui.isRunning() {
 		w.ui.setInitWindowFloating(floating)
 		return
@@ -101,7 +101,7 @@ func (w *window) SetFloating(floating bool) {
 	})
 }
 
-func (w *window) IsMaximized() bool {
+func (w *Window) IsMaximized() bool {
 	if !w.ui.isRunning() {
 		return w.ui.isInitWindowMaximized()
 	}
@@ -112,7 +112,7 @@ func (w *window) IsMaximized() bool {
 	return v
 }
 
-func (w *window) Maximize() {
+func (w *Window) Maximize() {
 	if !w.IsResizable() {
 		panic("ui: a window to maximize must be resizable")
 	}
@@ -123,7 +123,7 @@ func (w *window) Maximize() {
 	w.ui.t.Call(w.ui.maximizeWindow)
 }
 
-func (w *window) IsMinimized() bool {
+func (w *Window) IsMinimized() bool {
 	if !w.ui.isRunning() {
 		return false
 	}
@@ -134,7 +134,7 @@ func (w *window) IsMinimized() bool {
 	return v
 }
 
-func (w *window) Minimize() {
+func (w *Window) Minimize() {
 	if !w.ui.isRunning() {
 		// Do nothing
 		return
@@ -142,7 +142,7 @@ func (w *window) Minimize() {
 	w.ui.t.Call(w.ui.iconifyWindow)
 }
 
-func (w *window) Restore() {
+func (w *Window) Restore() {
 	if !w.ui.isRunning() {
 		// Do nothing
 		return
@@ -150,7 +150,7 @@ func (w *window) Restore() {
 	w.ui.t.Call(w.ui.restoreWindow)
 }
 
-func (w *window) Position() (int, int) {
+func (w *Window) Position() (int, int) {
 	if !w.ui.isRunning() {
 		panic("ui: WindowPosition can't be called before the main loop starts")
 	}
@@ -173,7 +173,7 @@ func (w *window) Position() (int, int) {
 	return x, y
 }
 
-func (w *window) SetPosition(x, y int) {
+func (w *Window) SetPosition(x, y int) {
 	if !w.ui.isRunning() {
 		w.ui.setInitWindowPositionInDIP(x, y)
 		return
@@ -183,7 +183,7 @@ func (w *window) SetPosition(x, y int) {
 	})
 }
 
-func (w *window) Size() (int, int) {
+func (w *Window) Size() (int, int) {
 	if !w.ui.isRunning() {
 		ww, wh := w.ui.getInitWindowSizeInDIP()
 		return w.ui.adjustWindowSizeBasedOnSizeLimitsInDIP(ww, wh)
@@ -196,7 +196,7 @@ func (w *window) Size() (int, int) {
 	return ww, wh
 }
 
-func (w *window) SetSize(width, height int) {
+func (w *Window) SetSize(width, height int) {
 	if !w.ui.isRunning() {
 		w.ui.setInitWindowSizeInDIP(width, height)
 		return
@@ -212,11 +212,11 @@ func (w *window) SetSize(width, height int) {
 	})
 }
 
-func (w *window) SizeLimits() (minw, minh, maxw, maxh int) {
+func (w *Window) SizeLimits() (minw, minh, maxw, maxh int) {
 	return w.ui.getWindowSizeLimitsInDIP()
 }
 
-func (w *window) SetSizeLimits(minw, minh, maxw, maxh int) {
+func (w *Window) SetSizeLimits(minw, minh, maxw, maxh int) {
 	if !w.ui.setWindowSizeLimitsInDIP(minw, minh, maxw, maxh) {
 		return
 	}
@@ -227,12 +227,12 @@ func (w *window) SetSizeLimits(minw, minh, maxw, maxh int) {
 	w.ui.t.Call(w.ui.updateWindowSizeLimits)
 }
 
-func (w *window) SetIcon(iconImages []image.Image) {
+func (w *Window) SetIcon(iconImages []image.Image) {
 	// The icons are actually set at (*UserInterface).loop.
 	w.ui.setIconImages(iconImages)
 }
 
-func (w *window) SetTitle(title string) {
+func (w *Window) SetTitle(title string) {
 	if !w.ui.isRunning() {
 		w.ui.m.Lock()
 		w.ui.title = title
@@ -245,14 +245,14 @@ func (w *window) SetTitle(title string) {
 	})
 }
 
-func (w *window) IsBeingClosed() bool {
+func (w *Window) IsBeingClosed() bool {
 	return w.ui.isWindowBeingClosed()
 }
 
-func (w *window) SetClosingHandled(handled bool) {
+func (w *Window) SetClosingHandled(handled bool) {
 	w.ui.setWindowClosingHandled(handled)
 }
 
-func (w *window) IsClosingHandled() bool {
+func (w *Window) IsClosingHandled() bool {
 	return w.ui.isWindowClosingHandled()
 }
diff --git a/internal/ui/window_null.go b/internal/ui/window_null.go
new file mode 100644
index 000000000..059eda1d4
--- /dev/null
+++ b/internal/ui/window_null.go
@@ -0,0 +1,100 @@
+// Copyright 2022 The Ebiten Authors
+//
+// 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.
+
+//go:build android || js || ios || ebitencbackend
+// +build android js ios ebitencbackend
+
+package ui
+
+import (
+	"image"
+)
+
+type Window struct{}
+
+func (*Window) IsDecorated() bool {
+	return false
+}
+
+func (*Window) SetDecorated(decorated bool) {
+}
+
+func (*Window) IsResizable() bool {
+	return false
+}
+
+func (*Window) SetResizable(resizable bool) {
+}
+
+func (*Window) Position() (int, int) {
+	return 0, 0
+}
+
+func (*Window) SetPosition(x, y int) {
+}
+
+func (*Window) Size() (int, int) {
+	return 0, 0
+}
+
+func (*Window) SetSize(width, height int) {
+}
+
+func (*Window) SizeLimits() (minw, minh, maxw, maxh int) {
+	return -1, -1, -1, -1
+}
+
+func (*Window) SetSizeLimits(minw, minh, maxw, maxh int) {
+}
+
+func (*Window) IsFloating() bool {
+	return false
+}
+
+func (*Window) SetFloating(floating bool) {
+}
+
+func (*Window) Maximize() {
+}
+
+func (*Window) IsMaximized() bool {
+	return false
+}
+
+func (*Window) Minimize() {
+}
+
+func (*Window) IsMinimized() bool {
+	return false
+}
+
+func (*Window) SetIcon(iconImages []image.Image) {
+}
+
+func (*Window) SetTitle(title string) {
+}
+
+func (*Window) Restore() {
+}
+
+func (*Window) IsBeingClosed() bool {
+	return false
+}
+
+func (*Window) SetClosingHandled(handled bool) {
+}
+
+func (*Window) IsClosingHandled() bool {
+	return false
+}
diff --git a/window.go b/window.go
index c98e4c018..67e0f0a0f 100644
--- a/window.go
+++ b/window.go
@@ -31,10 +31,7 @@ const (
 //
 // IsWindowDecorated is concurrent-safe.
 func IsWindowDecorated() bool {
-	if w := ui.Get().Window(); w != nil {
-		return w.IsDecorated()
-	}
-	return false
+	return ui.Get().Window().IsDecorated()
 }
 
 // SetWindowDecorated sets the state if the window is decorated.
@@ -49,9 +46,7 @@ func IsWindowDecorated() bool {
 //
 // SetWindowDecorated is concurrent-safe.
 func SetWindowDecorated(decorated bool) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetDecorated(decorated)
-	}
+	ui.Get().Window().SetDecorated(decorated)
 }
 
 // IsWindowResizable reports whether the window is resizable by the user's dragging on desktops.
@@ -59,10 +54,7 @@ func SetWindowDecorated(decorated bool) {
 //
 // IsWindowResizable is concurrent-safe.
 func IsWindowResizable() bool {
-	if w := ui.Get().Window(); w != nil {
-		return w.IsResizable()
-	}
-	return false
+	return ui.Get().Window().IsResizable()
 }
 
 // SetWindowResizable sets whether the window is resizable by the user's dragging on desktops.
@@ -77,9 +69,7 @@ func IsWindowResizable() bool {
 //
 // SetWindowResizable is concurrent-safe.
 func SetWindowResizable(resizable bool) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetResizable(resizable)
-	}
+	ui.Get().Window().SetResizable(resizable)
 }
 
 // SetWindowTitle sets the title of the window.
@@ -88,9 +78,7 @@ func SetWindowResizable(resizable bool) {
 //
 // SetWindowTitle is concurrent-safe.
 func SetWindowTitle(title string) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetTitle(title)
-	}
+	ui.Get().Window().SetTitle(title)
 }
 
 // SetWindowIcon sets the icon of the game window.
@@ -114,9 +102,7 @@ func SetWindowTitle(title string) {
 //
 // SetWindowIcon is concurrent-safe.
 func SetWindowIcon(iconImages []image.Image) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetIcon(iconImages)
-	}
+	ui.Get().Window().SetIcon(iconImages)
 }
 
 // WindowPosition returns the window position.
@@ -131,10 +117,7 @@ func SetWindowIcon(iconImages []image.Image) {
 //
 // WindowPosition is concurrent-safe.
 func WindowPosition() (x, y int) {
-	if w := ui.Get().Window(); w != nil {
-		return w.Position()
-	}
-	return 0, 0
+	return ui.Get().Window().Position()
 }
 
 // SetWindowPosition sets the window position.
@@ -148,9 +131,7 @@ func WindowPosition() (x, y int) {
 // SetWindowPosition is concurrent-safe.
 func SetWindowPosition(x, y int) {
 	atomic.StoreUint32(&windowPositionSetExplicitly, 1)
-	if w := ui.Get().Window(); w != nil {
-		w.SetPosition(x, y)
-	}
+	ui.Get().Window().SetPosition(x, y)
 }
 
 var (
@@ -158,16 +139,11 @@ var (
 )
 
 func initializeWindowPositionIfNeeded(width, height int) {
-	w := ui.Get().Window()
-	if w == nil {
-		return
-	}
-
 	if atomic.LoadUint32(&windowPositionSetExplicitly) == 0 {
 		sw, sh := ui.Get().ScreenSizeInFullscreen()
 		x := (sw - width) / 2
 		y := (sh - height) / 3
-		w.SetPosition(x, y)
+		ui.Get().Window().SetPosition(x, y)
 	}
 }
 
@@ -178,10 +154,7 @@ func initializeWindowPositionIfNeeded(width, height int) {
 //
 // WindowSize is concurrent-safe.
 func WindowSize() (int, int) {
-	if w := ui.Get().Window(); w != nil {
-		return w.Size()
-	}
-	return 0, 0
+	return ui.Get().Window().Size()
 }
 
 // SetWindowSize sets the window size on desktops.
@@ -196,9 +169,7 @@ func SetWindowSize(width, height int) {
 	if width <= 0 || height <= 0 {
 		panic("ebiten: width and height must be positive")
 	}
-	if w := ui.Get().Window(); w != nil {
-		w.SetSize(width, height)
-	}
+	ui.Get().Window().SetSize(width, height)
 }
 
 // WindowSizeLimits returns the limitation of the window size on desktops.
@@ -206,10 +177,7 @@ func SetWindowSize(width, height int) {
 //
 // WindowSizeLimits is concurrent-safe.
 func WindowSizeLimits() (minw, minh, maxw, maxh int) {
-	if w := ui.Get().Window(); w != nil {
-		return w.SizeLimits()
-	}
-	return -1, -1, -1, -1
+	return ui.Get().Window().SizeLimits()
 }
 
 // SetWindowSizeLimits sets the limitation of the window size on desktops.
@@ -217,9 +185,7 @@ func WindowSizeLimits() (minw, minh, maxw, maxh int) {
 //
 // SetWindowSizeLimits is concurrent-safe.
 func SetWindowSizeLimits(minw, minh, maxw, maxh int) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetSizeLimits(minw, minh, maxw, maxh)
-	}
+	ui.Get().Window().SetSizeLimits(minw, minh, maxw, maxh)
 }
 
 // IsWindowFloating reports whether the window is always shown above all the other windows.
@@ -228,10 +194,7 @@ func SetWindowSizeLimits(minw, minh, maxw, maxh int) {
 //
 // IsWindowFloating is concurrent-safe.
 func IsWindowFloating() bool {
-	if w := ui.Get().Window(); w != nil {
-		return w.IsFloating()
-	}
-	return false
+	return ui.Get().Window().IsFloating()
 }
 
 // SetWindowFloating sets the state whether the window is always shown above all the other windows.
@@ -243,9 +206,7 @@ func IsWindowFloating() bool {
 //
 // SetWindowFloating is concurrent-safe.
 func SetWindowFloating(float bool) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetFloating(float)
-	}
+	ui.Get().Window().SetFloating(float)
 }
 
 // MaximizeWindow maximizes the window.
@@ -259,9 +220,7 @@ func MaximizeWindow() {
 	if !IsWindowResizable() {
 		panic("ebiten: a window to maximize must be resizable")
 	}
-	if w := ui.Get().Window(); w != nil {
-		w.Maximize()
-	}
+	ui.Get().Window().Maximize()
 }
 
 // IsWindowMaximized reports whether the window is maximized or not.
@@ -275,10 +234,7 @@ func IsWindowMaximized() bool {
 	if !IsWindowResizable() {
 		return false
 	}
-	if w := ui.Get().Window(); w != nil {
-		return w.IsMaximized()
-	}
-	return false
+	return ui.Get().Window().IsMaximized()
 }
 
 // MinimizeWindow minimizes the window.
@@ -289,9 +245,7 @@ func IsWindowMaximized() bool {
 //
 // MinimizeWindow is concurrent-safe.
 func MinimizeWindow() {
-	if w := ui.Get().Window(); w != nil {
-		w.Minimize()
-	}
+	ui.Get().Window().Minimize()
 }
 
 // IsWindowMinimized reports whether the window is minimized or not.
@@ -300,10 +254,7 @@ func MinimizeWindow() {
 //
 // IsWindowMinimized is concurrent-safe.
 func IsWindowMinimized() bool {
-	if w := ui.Get().Window(); w != nil {
-		return w.IsMinimized()
-	}
-	return false
+	return ui.Get().Window().IsMinimized()
 }
 
 // RestoreWindow restores the window from its maximized or minimized state.
@@ -315,9 +266,7 @@ func RestoreWindow() {
 	if !IsWindowMaximized() && !IsWindowMinimized() {
 		panic("ebiten: RestoreWindow must be called on a maximized or a minimized window")
 	}
-	if w := ui.Get().Window(); w != nil {
-		w.Restore()
-	}
+	ui.Get().Window().Restore()
 }
 
 // IsWindowBeingClosed returns true when the user is trying to close the window on desktops.
@@ -328,10 +277,7 @@ func RestoreWindow() {
 //
 // IsWindowBeingClosed is concurrent-safe.
 func IsWindowBeingClosed() bool {
-	if w := ui.Get().Window(); w != nil {
-		return w.IsBeingClosed()
-	}
-	return false
+	return ui.Get().Window().IsBeingClosed()
 }
 
 // SetWindowClosingHandled sets whether the window closing is handled or not on desktops. The default state is false.
@@ -346,9 +292,7 @@ func IsWindowBeingClosed() bool {
 //
 // SetWindowClosingHandled is concurrent-safe.
 func SetWindowClosingHandled(handled bool) {
-	if w := ui.Get().Window(); w != nil {
-		w.SetClosingHandled(handled)
-	}
+	ui.Get().Window().SetClosingHandled(handled)
 }
 
 // IsWindowClosingHandled reports whether the window closing is handled or not on desktops by SetWindowClosingHandled.
@@ -357,8 +301,5 @@ func SetWindowClosingHandled(handled bool) {
 //
 // IsWindowClosingHandled is concurrent-safe.
 func IsWindowClosingHandled() bool {
-	if w := ui.Get().Window(); w != nil {
-		return w.IsClosingHandled()
-	}
-	return false
+	return ui.Get().Window().IsClosingHandled()
 }