Day 004-Calculator

Making my first calculator for iphone 6 which offers 2 unique features
Color-to distinguish between all calculation prominently
Bracket option- for eg:user can click on '+' twice and get his whole calculation in bracket clicking thrice brings back to normal '+'

Please give your comments and suggestions as it is daily art bracket still needs some working upon.
Topics by http://eepurl.com/bBJdCD