Playing on a phone
The site works in the phone browser. Tap a cell, then pick a mark. The grid is the same one you get at a desk.
Use Notes when a tap would otherwise force a guess. A short session fits a phone: one Beginner board, or a few minutes on a board you already started.
Turn the phone if you want more room. The cells stay large enough to tap.
Leave the puzzle and Continue later. The board stays in this browser. Home, Play, and Solved are the same on a phone as on a desk.