Sum-o is a simple and practical calculator app. If you like minimal design and gesture control, the iOS app may suit for you.
Sum-o is designed for both iPhone and iPad, and shows off an elegant and minimalistic user interface. Unlike most calculator apps, Sum-o hides computing symbols in a slidable icon in order to match its minimal design, so you need to slide or tap the icon for these symbols, moreover, the calculator app also features easy-to-use gesture controls such as pulling down or shaking for answers, pulling up for clearing, swiping right for checking previous calculations, and etc. Apart from that its color changes according to your calculations.
Sum-o is available for free at present. If you need the iOS app, head to App Store for download.