FutureCalc: ergonomic calculator for single-handed use

FutureCalc is an ergonomic calculator, possibly the first of its kind, specifically designed for single-handed use. All buttons are accessible for the thumb without repositioning the phone or supporting it with the other hand.
Two layouts are available to choose from: we call them Radial and Concave. Each can be flipped for either right or left hand use.
Features:
- No equal sign: the results are displayed "on the fly", so no need for an extra tap.
- The basic set of arithmetic operations: addition, subtraction, multiplication, division; the internal format is 64-bit floating point.
- Flip the keypad for use with either left or right hand using the button with two arrows.
- Switch the designs using the settings button at the bottom.
- There is only one CLEAR button: tap once to delete a digit, or tap and hold for a second to reset the calculator.
- Copy/paste supported: tap on any of the displayed numbers; the editable number allows copy and paste, while others are only copyable.
- Maximum length for arguments in this version is 16 digits.
- Works on all iPhones starting from 4S. The 6/6S design is adjusted so that the physical size of the buttons is the same.
Enjoy your numbers!