I make these on MIT App Inventor... here's my gallery and here's where to go to make your own.
For students of the Suzuki Violin Method: suggested daily review lists, track your practice... and watch ANY piece played on You Tube.
Here's a link for the APP download - an APK file to install on your phone.
And here's the pdf overview.
Work out the patterns to ... remove the red squares.
Here's the Android APK file to run this on your phone.
Pitch and tilt your phone to make the balls hit a target.
Here's a version you can download (Android only) - open this APK file with your phone.