diff --git a/backends/x/x.go b/backends/x/x.go
index cdea721..bd6cb15 100644
--- a/backends/x/x.go
+++ b/backends/x/x.go
@@ -31,6 +31,7 @@ type Backend struct {
 func NewBackend () (output tomo.Backend, err error) {
 	backend := &Backend {
 		windows: map[xproto.Window] *Window { },
+		doChannel: make(chan func (), 0),
 	}
 	
 	// connect to X
@@ -51,10 +52,12 @@ func (backend *Backend) Run () (err error) {
 	pingQuit := xevent.MainPing(backend.connection)
 	for {
 		select {
-		case <- pingBefore: <- pingAfter
+		case <- pingBefore:
+			<- pingAfter
 		case callback := <- backend.doChannel:
 			callback()
-		case <- pingQuit: return
+		case <- pingQuit:
+			return
 		}
 	}
 }
diff --git a/elements/basic/progressbar.go b/elements/basic/progressbar.go
new file mode 100644
index 0000000..6ac9778
--- /dev/null
+++ b/elements/basic/progressbar.go
@@ -0,0 +1,56 @@
+package basic
+
+import "image"
+import "git.tebibyte.media/sashakoshka/tomo/theme"
+import "git.tebibyte.media/sashakoshka/tomo/artist"
+import "git.tebibyte.media/sashakoshka/tomo/elements/core"
+
+// ProgressBar displays a visual indication of how far along a task is.
+type ProgressBar struct {
+	*core.Core
+	core core.CoreControl
+	progress float64
+}
+
+// NewProgressBar creates a new progress bar displaying the given progress
+// level.
+func NewProgressBar (progress float64) (element *ProgressBar) {
+	element = &ProgressBar { progress: progress }
+	element.Core, element.core = core.NewCore(element)
+	element.core.SetMinimumSize(theme.Padding() * 2, theme.Padding() * 2)
+	return
+}
+
+// Resize resizes the progress bar.
+func (element *ProgressBar) Resize (width, height int) {
+	element.core.AllocateCanvas(width, height)
+	element.draw()
+	return
+}
+
+// SetProgress sets the progress level of the bar.
+func (element *ProgressBar) SetProgress (progress float64) {
+	if progress == element.progress { return }
+	element.progress = progress
+	if element.core.HasImage() {
+		element.draw()
+		element.core.PushAll()
+	}
+}
+
+func (element *ProgressBar) draw () {
+	bounds := element.core.Bounds()
+
+	artist.FillRectangle (
+		element.core,
+		theme.SunkenPattern(),
+		bounds)
+	meterBounds := image.Rect (
+		bounds.Min.X + 2, bounds.Min.Y + 2,
+		bounds.Min.X - 1 + int(float64(bounds.Dx()) * element.progress),
+		bounds.Dy() - 1)
+	artist.FillRectangle (
+		element.core,
+		theme.AccentPattern(),
+		meterBounds)
+}
diff --git a/examples/goroutines/main.go b/examples/goroutines/main.go
index 9fc02c6..f0253f7 100644
--- a/examples/goroutines/main.go
+++ b/examples/goroutines/main.go
@@ -35,8 +35,10 @@ func formatTime () (timeString string) {
 
 func tick (label *basic.Label, clock *fun.AnalogClock) {
 	for {
-		label.SetText(formatTime())
-		clock.SetTime(time.Now())
+		tomo.Do (func () {
+			label.SetText(formatTime())
+			clock.SetTime(time.Now())
+		})
 		time.Sleep(time.Second)
 	}
 }
diff --git a/examples/progress/main.go b/examples/progress/main.go
new file mode 100644
index 0000000..97c3ff2
--- /dev/null
+++ b/examples/progress/main.go
@@ -0,0 +1,40 @@
+package main
+
+import "time"
+import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
+import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
+import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
+
+func main () {
+	tomo.Run(run)
+}
+
+func run () {
+	window, _ := tomo.NewWindow(2, 2)
+	window.SetTitle("Approaching")
+	container := basic.NewContainer(layouts.Vertical { true, true })
+	window.Adopt(container)
+
+	container.Adopt (basic.NewLabel (
+		"Rapidly approaching your location...", false), false)
+	bar := basic.NewProgressBar(0)
+	container.Adopt(bar, false)
+	button := basic.NewButton("Stop")
+	button.SetEnabled(false)
+	container.Adopt(button, false)
+	
+	window.OnClose(tomo.Stop)
+	window.Show()
+	go fill(bar)
+}
+
+func fill (bar *basic.ProgressBar) {
+	println("-")
+	for progress := 0.0; progress < 1.0; progress += 0.01 {
+		time.Sleep(time.Second / 24)
+		tomo.Do(func () {
+			bar.SetProgress(progress)
+		})
+	}
+}