This is a simple circular sliderule simulator you can use. Use the mouse wheel while you have your mouse outside of the face to move the hand. Holding shift makes it go slower. Using the wheel inside the face moves the face. Click outside the face to register the inner face to the hand. Click again to register to the origin. Click inside the face to set the origin to the hand. Touch on mobile works as well. The Gauge marks are as follows: π ~ 3.1416 is clear, e ~ 2.71828 as well, c ~ 1.128 marks sqrt(4/pi) the circle constant for finding areas of circles given their diameter. L marks the natural log of 10 ~ 2.3026. r ~ 57.3 is the number of degrees in a radian, and Q ~ 0.01745 is the number of radians in a degree.