- There is only portrait orientation and no landscape orientation.
- The navigation buttons ("<", ">") do not seem to function well as I often have to click it a few times before the previous/next puzzle is shown.
- In fact, the Statistics page could be made clickable with hyperlinks to directly go to a puzzle (Easy, Medium and Hard).
- The numerical pad for data entry should be a 3x3 array matrix instead of in 2 rows.
- In the puzzle itself, the last column on the right-hand side does not accept the click very well because I have to push it a few times before a number gets entered.
- When the "Start" button is clicked, the option panel with Easy, Medium and Hard should show up instead of defaulting to Easy and having to click the "New" button.
- Since some pencil numbers are really small, especially in Butterfly Sudoku and Twodoku, I would like to see that 2-finger gesture can zoom in to magnify certain areas of interest.
- The original numbers should stay solid, not to be deleted or overwritten by accidentally clicking another number. There is no way of undoing a mistake, so the puzzle is spoiled if you do not remember the original number.
- As "Undo" is essential, maybe clicking the "Trash" button once would undo an action, twice would really trash it?
- Solid extra lines (Argyle Sudoku, Sudoku X) and grey shades (Asterisk Sudoku, Centre Dot Sudoku, Even-Odd Sudoku, Girandola Sudoku, Windoku) obscure the numbers, so the lines and the shades could be shown in different colours.
- The light watermark image sometimes makes small pencil numbers difficult to read, so the image could be removed.
- The Reset button on the Statistics page should ask if it is really OK to reset the stats.
- There could be a pen button and a pencil button for Binary Puzzle. I ended up using a non-permanent marker on my iPhone's screen!
- Argyle Sudoku (Hard) is simply too hard. I have solved thousands of Conceptis Sudoku puzzles over 10+ years without making any guesses and written a book "Take Control of Sudoku (3-by-3 Sub-grid Exhaustive Elimination Method)", but I had to guess for the first time in my life to solve one Argyle Sudoku (Hard) puzzle after failing to solve about 20 puzzles in a row.
- The 2 screenshots below show Twodoku with my answer (first image with GREEN circles) and the app's solution after clicking the "Solve" button (second image with RED circles). Not only was my correct answer not recognized, but also the app's solution is wrong. It is not an isolated case but happens every time in Medium and Hard. Thus, Twodoku (Medium, Hard) remains the only puzzle that I could not change from "0" in Statistics.
