Mission 4: Calculator

For the 4th DailyUI challenge, I have been working on a calculator designed for children. Concerning the UI, it was the opportunity to play around with 3D effects and inner shadows.
Regarding the UX, I had some interesting readings on my way. Check it out :
- http://uxmovement.com/thinking/why-calculators-need-a-better-user-interface/

Feedbacks are welcome!