diff --git a/image.go b/image.go
index 8229b429e..f18479799 100644
--- a/image.go
+++ b/image.go
@@ -25,7 +25,7 @@ import (
 
 	"github.com/hajimehoshi/ebiten/internal/graphics"
 	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
-	"github.com/hajimehoshi/ebiten/internal/ui"
+	"github.com/hajimehoshi/ebiten/internal/loop"
 )
 
 var (
@@ -296,7 +296,7 @@ func (i *imageImpl) DrawImage(image *Image, options *DrawImageOptions) error {
 }
 
 func (i *imageImpl) At(x, y int) color.Color {
-	if !ui.IsRunning() {
+	if !loop.IsRunning() {
 		panic("ebiten: At can't be called when the GL context is not initialized (this panic happens as of version 1.4.0-alpha)")
 	}
 	imageM.Lock()
diff --git a/internal/ui/run.go b/internal/loop/run.go
similarity index 87%
rename from internal/ui/run.go
rename to internal/loop/run.go
index c51ec2731..7f8b07101 100644
--- a/internal/ui/run.go
+++ b/internal/loop/run.go
@@ -12,16 +12,22 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package ui
+package loop
 
 import (
 	"errors"
 	"sync"
 	"time"
+
+	"github.com/hajimehoshi/ebiten/internal/ui"
 )
 
 const FPS = 60
 
+func Main() {
+	ui.Main()
+}
+
 func CurrentFPS() float64 {
 	return currentRunContext.currentFPS()
 }
@@ -43,7 +49,7 @@ func SetScreenScale(scale int) error {
 }
 
 func ScreenScale() int {
-	return currentUI.ScreenScale()
+	return ui.CurrentUI().ScreenScale()
 }
 
 type runContext struct {
@@ -116,16 +122,16 @@ func (c *runContext) updateScreenSize(g GraphicsContext) error {
 	}
 	changed := false
 	if 0 < c.newScreenWidth || 0 < c.newScreenHeight {
-		c := currentUI.SetScreenSize(c.newScreenWidth, c.newScreenHeight)
+		c := ui.CurrentUI().SetScreenSize(c.newScreenWidth, c.newScreenHeight)
 		changed = changed || c
 	}
 	if 0 < c.newScreenScale {
-		c := currentUI.SetScreenScale(c.newScreenScale)
+		c := ui.CurrentUI().SetScreenScale(c.newScreenScale)
 		changed = changed || c
 	}
 	if changed {
 		w, h := c.newScreenWidth, c.newScreenHeight
-		if err := g.SetSize(w, h, currentUI.ActualScreenScale()); err != nil {
+		if err := g.SetSize(w, h, ui.CurrentUI().ActualScreenScale()); err != nil {
 			return err
 		}
 	}
@@ -171,32 +177,32 @@ func Run(g GraphicsContext, width, height, scale int, title string) error {
 	currentRunContext.startRunning()
 	defer currentRunContext.endRunning()
 
-	if err := currentUI.Start(width, height, scale, title); err != nil {
+	if err := ui.CurrentUI().Start(width, height, scale, title); err != nil {
 		return err
 	}
-	defer currentUI.Terminate()
+	defer ui.CurrentUI().Terminate()
 
-	if err := g.SetSize(width, height, currentUI.ActualScreenScale()); err != nil {
+	if err := g.SetSize(width, height, ui.CurrentUI().ActualScreenScale()); err != nil {
 		return err
 	}
 
 	frames := 0
-	n := Now()
+	n := ui.Now()
 	beforeForUpdate := n
 	beforeForFPS := n
 	for {
 		if err := currentRunContext.updateScreenSize(g); err != nil {
 			return err
 		}
-		e, err := currentUI.Update()
+		e, err := ui.CurrentUI().Update()
 		if err != nil {
 			return err
 		}
 		switch e.(type) {
-		case CloseEvent:
+		case ui.CloseEvent:
 			return nil
-		case RenderEvent:
-			now := Now()
+		case ui.RenderEvent:
+			now := ui.Now()
 			// If beforeForUpdate is too old, we assume that screen is not shown.
 			if int64(5*time.Second/FPS) < now-beforeForUpdate {
 				currentRunContext.setRunningSlowly(false)
@@ -216,7 +222,7 @@ func Run(g GraphicsContext, width, height, scale int, title string) error {
 						return err
 					}
 				}
-				currentUI.SwapBuffers()
+				ui.CurrentUI().SwapBuffers()
 				beforeForUpdate += int64(tt) * int64(time.Second) / FPS
 				frames++
 			}
diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index 577708863..9bf5ec4ad 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -43,6 +43,10 @@ type UserInterface struct {
 
 var currentUI *UserInterface
 
+func CurrentUI() *UserInterface {
+	return currentUI
+}
+
 func Init() (*opengl.Context, error) {
 	runtime.LockOSThread()
 
diff --git a/run.go b/run.go
index 8b673791e..6cded7a5f 100644
--- a/run.go
+++ b/run.go
@@ -15,11 +15,11 @@
 package ebiten
 
 import (
-	"github.com/hajimehoshi/ebiten/internal/ui"
+	"github.com/hajimehoshi/ebiten/internal/loop"
 )
 
 // FPS represents how many times game updating happens in a second.
-const FPS = ui.FPS
+const FPS = loop.FPS
 
 // CurrentFPS returns the current number of frames per second of rendering.
 //
@@ -30,7 +30,7 @@ const FPS = ui.FPS
 // Note that logical game updating is assured to happen 60 times in a second
 // as long as the screen is active.
 func CurrentFPS() float64 {
-	return ui.CurrentFPS()
+	return loop.CurrentFPS()
 }
 
 // IsRunningSlowly returns true if the game is running too slowly to keep 60 FPS of rendering.
@@ -39,7 +39,7 @@ func CurrentFPS() float64 {
 //
 // This function is concurrent-safe.
 func IsRunningSlowly() bool {
-	return ui.IsRunningSlowly()
+	return loop.IsRunningSlowly()
 }
 
 // Run runs the game.
@@ -56,9 +56,9 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 	ch := make(chan error)
 	go func() {
 		g := newGraphicsContext(f)
-		ch <- ui.Run(g, width, height, scale, title)
+		ch <- loop.Run(g, width, height, scale, title)
 	}()
-	ui.Main()
+	loop.Main()
 	return <-ch
 }
 
@@ -67,7 +67,7 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 //
 // This function is concurrent-safe.
 func SetScreenSize(width, height int) {
-	if err := ui.SetScreenSize(width, height); err != nil {
+	if err := loop.SetScreenSize(width, height); err != nil {
 		panic(err)
 	}
 }
@@ -76,7 +76,7 @@ func SetScreenSize(width, height int) {
 //
 // This function is concurrent-safe.
 func SetScreenScale(scale int) {
-	if err := ui.SetScreenScale(scale); err != nil {
+	if err := loop.SetScreenScale(scale); err != nil {
 		panic(err)
 	}
 }
@@ -85,5 +85,5 @@ func SetScreenScale(scale int) {
 //
 // This function is concurrent-safe.
 func ScreenScale() int {
-	return ui.ScreenScale()
+	return loop.ScreenScale()
 }