Knothole

Knothole is a wooden tilt maze, like the box with two knobs you may remember: a steel marble rolls around a honey-coloured board, past walls and through a scatter of holes, to the goal. It is built to be learned in ten seconds. The first level has no holes at all, and each level after it adds one new trouble, up to a last board with thirty-one holes.

You can tilt however suits the device. On a phone, tilt the phone itself (iPhones ask permission once, on a tap, and a Reset flat button sets "level" to however you are holding it). On a laptop, move the mouse and the board leans toward the cursor, or use the arrow keys or WASD. On a touch screen without a motion sensor, drag a finger on the board. The board can only tilt a little and tilts at the speed a hand could, so the marble has weight and quick flicks fling it.

Nothing needs an account, and most of the ways to play are against someone. Race the computer, who plays the same board by the same rules at easy, medium or hard. Share one screen with a friend (one uses WASD, the other the arrow keys). Watch two computer players of different skill race each other. Or finish a run, press "Challenge a friend", and send the link: your friend opens it, plays the same level and finds out whether they beat your time.