DailyUI #004 - Calculator

Hey dribbble!
Here is my shot for daily ui #004, where we were to create a calculator of any kind. I ended up creating a simple mobile app calculator interface that felt clean and easy to use. I emphasized important buttons and information as I understand that many people use calculators in a rush. I also provided a history tab so that the user will not lose previous calculations.
I gave myself limited time to complete this challenge, forcing myself to make quick decisions.
What do you think?
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