Level

The level measures the tilt of the phone itself, resting on a surface. Its reference edge is the long side of the body, 150–165 mm on an ordinary phone: many times shorter than a builder's level, so a small error at the phone becomes a large one at the far end of a board. The exact length for this phone is named at the top of the instrument. Calibration here does not need a flat surface: two readings a half-turn apart cancel the tilt of whatever it lies on.

The instrument uses the phone's gravity sensor and shows the value in °.

• A bullseye when the phone is flat — both axes at once.

• A tube when the phone stands on an edge.

• The screen goes green and the phone buzzes at zero.

• One-tap calibration: a case and the camera bump are subtracted.

• No ads. Under a megabyte. Works without internet.

The app sends anonymous usage statistics; you can turn this off in settings.

Independent development: one person builds and maintains this app. A letter to xmaxxp@gmail.com is read by that person, not by a support desk.