For a harder challenge, make it so that you can use a second finger to rotate your rectangles. To do this, you will need to handle multiple pointers in your MotionEvent handling code. You will also need to rotate your canvas.

When dealing with multiple touches, you need these extra ideas:

The pointer index may change, but the pointer ID will not.

For more details, check out the documentation for the following MotionEvent methods:

    public final int getActionMasked()
    public final int getActionIndex()
    public final int getPointerId(int pointerIndex)
    public final float getX(int pointerIndex)
    public final float getY(int pointerIndex)

Also look at the documentation for the ACTION_POINTER_UP and ACTION_POINTER_DOWN constants.