Its a mini calculator with simple functions- addition,subtraction, multiplication and division. I have focused particulaly on the UI. Some of the UI features are-

1. The size of the text increases and decreases depending upon the active field. For eg if you are writing the equation the equation size would increase and soution size would decrease and vice versa

2. The different size button. The equal button is 2x then the rest of them and sign is in the middle.

3. Both horizontal and vertical view possible