Simple Scientific Calculator adhering to the style of the early 1980s. Easy to use and familiar for those of us from that era. Adds a touch of realism in look and feel, layout, key click sounds, LCD display digits and response. Functions and operations are as you're used to, but adds a few more features that you'd wished you'd had back then, to give you a modern day usable device. Quick Help: • Green [INV] button (upper left) is the "shift" or "2nd" function button. • Press and hold the blue [MODE] (HELP) button for web-based help.