SudokuSmart iOS - Free Sudoku App with advanced levels and hints

For a school project, I started exploring ways to solve sudokus with code. At the time, I found that existing mainstream sudoku apps had many advertisements, and often failed to teach me new solving methods. I decided to build a mobile interface onto which you could input any sudoku grid and recieve steps on how to solve it. It was a successful school project, and so I decided to pursue publishing on the App Store. Six months later, SudokuSmart 1.0 was launched, albeit with many issues. Another six months has passed since then, and, as I leave school, the app has finally fulfilled its purpose of improving significantly on mainstream sudoku apps. Any feedback would be highly appreciated, as the app is constantly improving.