Calculator - Daily UI 004

Hi everyone. This shot is exercise "DailyUI 004" in DailyUI challenge.
Design Hint: Design a calculator. Standard, scientific, or specialty calculator for something such as a mortgage? Is it for a phone, a tablet, a web app?
Thanks @Muhammad Fatih Takey give me inspiration to make this shot.
- I'm just learning, so i hope everyone help me to improve UI design. Thanks a lot!