A SIMPLE CALCULATOR
**** Added KeyBoard Functionality ****
For easter egg, hover over to 'Let's Calculate.'
Added extra functions like square root, sine, cosine and tan
Guide for using calculator
1. To use square root button from KeyBoard, use key 'r'.
2. To use sine, press key 's' on keyboard.
3. To use cosine, press key 'c' on keyboard.
4. To use tan, press key 't' on keyboard.
5. To delete single character on screen, use backspace key.
6. To reset calculator screen, use esc key on keyboard.
7. The calculator has the precision of upto 6 decimal places.