The app will calculate angle precise like water bubble (Spirit Level) for free. Calculating an angle, slope has never been this easy. This application will make your life easier, you will no longer move a spirit level (Water bubble) with you. The app uses gyro to make calculations and it behave like real spirit level. The app will work both precise and accurate. Normally water bubbles are heavy to carry but with this app you don't have to carry it. Your water bubble in your pocket.