GTCalculator - Multi items sum

A grouped multi items sum calculator, getting the most out of touch screen area, easy to edit and select

Keyboard area usage:
= - confirm item imput
backspace - delete last active input
C - Save current calculation and create a new one

Calculation display area usage:
- tap numbers or operand to highlight and edit
- tap item cell result area to switch selection status (inclusion/exclusion)
- tap item title to edit
- long press item cell result part to switch subtraction status(+/-)
- tap the expression area to make it editable