var engine = new RainyDay({
    element: 'background',  // ID of image element
                            // This value is required
    parentElement: someDiv, // Element to be used as a parent for the canvas
                            // If not provided assuming the 'body' element
    crop: [ 0, 0, 50, 60],  // Coordinates if only a part of the image should be used
                            // If not provided entire image will be used
    blur: 10,               // Defines blur due to rain effect
                            // Assuming 10 if not provided
                            // Use 0 value to disable the blur
    opacity: 1,             // Opacity of rain drops
                            // Assuming 1 if not provided
    fps: 30                 // Frame rate per second
                            // This value is required
});
engine.rain([ [3, 3, 0.88], [5, 5, 0.9], [6, 2, 1] ], 100);