Zip Line Go

Start at 1. Draw through 2, then 3, then 4. Cover every square on the board. That's the whole rule, and it takes about ten seconds to learn. Then the boards get bigger. Some have two or three lines that have to share the space. Some numbers split, and you send a path off in each direction. Walls start getting in the way. By the big boards near the end, you'll stare at one corner for a minute before the move clicks, and that's the good part. There are 2,500 levels free. Once you've solved ten, the daily puzzle opens: a new board every day, cut into a different shape. Monday might be a moon, Sunday a big bell, and on Halloween it's a pumpkin. Keep a streak going if you like that sort of thing, or ignore it and just play. Solving also earns you skins. New line colours, shapes for the numbers, number fonts, grids, frames, the burst you get when you finish, and the sounds the lines make. Put…