In order for the website to work, you need to be on a laptop or desktop. The Web App will not run on a phone. Even if it did run on phone screen, it would be very hard to enter pixel values on a small phone screen. A larger screen is needed.
On the Mac OS X, the Web App runs on Safari, Firefox and Chrome. On Windows, the Web App runs on Google Chrome, Chromium, Microsoft Edge, and Opera. On Linux, it also works on Firefox and Chrome. In all cases, you need a browser that supports HTML 5.