It's true that phones don't have a whole ton of storage space. So you might want to remove a riff that you've watched from your phone once you're done with it! Doing so is easy - just tap the Play icon from the main menu, and you'll get to your list of riffs on your device. Tap the "Edit" link and then the "X" button for whichever riff you want to remove. You can always redownload it if you want to watch it again!