Every 100 years, the mysterious castle of Sudokuvania appears in the countryside. Legend has it that it contains the Secret of Sudoku. Gathering the last few given digits in the area, you solemnly approach the boxy fortress, determined to discover the secret and share it with your favorite people.
You should be able to zoom in/out by scrolling up/down
Nope, at least not on Firefox or edge.
Edit: You have to switch on large puzzle UI in experimental settings.