How to add a falling rain effect to video in real time online?

1. Upload a video you want to add  rain to  
2. Upload a rain transparent image   
3. The overlay image must be 2 times higher than the canvas height to make sure that it will be scrolling processed
4. The image will start scrolling up automatically by default
5. For faster scrolling speed move the mouse cursor to the canvas bottom right corner 
6. To slow down move the mouse cursor to the canvas top left corner
7. Start recording your video 
8. To scroll down move the mouse cursor to the canvas bottom left corner and hold the position
9. To remove the scrolling rain image move the mouse cursor out of the canvas
10. To restart the scrolling rain image over the video move the mouse cursor inside the canvas
11. Pause    your video
12.  Download your video    with a falling rain effect overlaid