ui: run in background

internal/ui/window.go

@@ -26,6 +26,8 @@ type Window struct {
 //
 // ebiten assumes a single window, so only call this once...
 func NewWindow(title string) (*Window, error) {
+	ebiten.SetRunnableInBackground(true)
+
 	return &Window{
 		Title:         title,
 		KeyUpHandlers: make(map[ebiten.Key]func()),