How to modify the width and background of cards in a Slider created using Swiffy Slider Plugin

I was trying to use the Swiffy Slider Plugin from Saq's Sandbox — Experimental doodads to create a slider for quickcapture in mobile by including some forms, todo and tracker tiddlers (and the same in a modal) based on the example shown here

I want to modify the CSS so that the cards occupy the maximum available area and also to change the background of the slider container. @saqimtiaz Can you please tell where are those two parameters defined in the stylesheet tiddler.