Surface Level 4 facilitates the measurement of the slope of whatever surface you want to check. This professional tool distinguishes itself from other similar apps by its slick design and the support to multiple types of units (degree, radian and gradian). More importantly, its accuracy is ensured at the maximum level by the support to different sensitivities that allow you to detect subtle slopes (pool billiard table, floor leveling or furniture arrangement). Features - Level surfaces in two directions at the same time - Support multiple angle units: degree, radian, gradian and slope - Easy and quick calibration function - Magnify the level reading by supporting different sensitivities (more sensitivity ~ small reading ~ low slope detection) - Sound follows the bubble positions for easier control and can be enabled/disabled - Lock and unlock modes - SPECIAL!!! Getting bored with the default bubble theme? Then you can change to the additional cool background with our mother earth and the galaxy -- CALIBRATION INSTRUCTION -- 1. Put your iPhone/iPod touch on a flat surface or table (its back lies on the surface/table) 2. Press "calibration" button located at the bottom-right of the screen To make your device work more accurately, calibrate the level before use.