I made an on-line Sudoku game named Sudoffle. Sudoffle It's only 7 days old, hence the Beta in the title. I don't know of any current bugs, but I'm still adding new features.
It's pretty vanilla Sudoku, except that you get a few 'yellow clues' as well as the regular (green) clues at the start. The yellow clues (if any) show a wrong number for that square. If you're on a PC, you can navigate using the cursor keys, with number keys making a guess and space/backspace/delete removing a guess. If you prefer, you can use the mouse - and if you're playing on a phone or tablet, then you just tap.
When you complete a row, column or block, then it's coloured in with green for correct squares and yellow for any wrong guesses. If you make a conflicted guess (a number that already appears non-yellow in the same row, column, or block) then your guess is shaded grey, and you're locked on that square until you change or delete your guess.
At the end, you get a Wordle-style score you can share, if you want.
There's a new puzzle each day (changes at midnight UTC). I'm slowly adding new features, one of which will allow you to play puzzles other than the one of the day. I also plan to add an (optional) automatic 'pencil marks' thing, better statistics, selectable colour themes and such.
I'll be grateful for any feedback.