Simple Calculator

A very slim and simple calculator. My idea was to have a 4x4 layout with just 3 operators (minus, plus, multiply here) right at hand. If you needed access to more operators you just swipe up/down on the column. At the first few starts you have a stroke around the column you can swipe on, but later on it'll reduce the opacity of the stroke to zero, based on an idea I've recently read in an article (will add the link later). The Idea was basically to get the user used to the UI and then continuously remove unnecessary elements. See attachments for a better understanding :).