A point of origin for a polar coordinate system is called a pole. A polar axis is a closed half-line with the pole as a vertex and defined unit segments.
Each point in a polar system is associated with pair or numbers (ρ; φ). The coordinate ρ is a distance from the pole to the point. The coordinate φ is an angle between the polar axis and a segment connected the pole and the point. The angle is positive if it is clockwise and negative if counterclockwise.
Note that the angle is ambiguously determined because pairs of numbers (ρ; φ+2πn) correspond to the one point in the polar system.
The model is a shooting game. You have a target (green point at the radar). Set its coordinate (Distance and Angle) and click the Fire button. A missile is launched to the reference point. If you hit the mark then the green point become a padded UFO and a score is increased. A next target of 12 is appeared. A statistics of your shots is showed as 12 pictures. A picture with UFO corresponds to a future target, while a puff of smoke shows a destroyed target. A picture without UFO is a missed target. A sandglass is appeared if your time for a shot is expired. You can select a level of the game. There are Newbie, Advanced and Professional. The Newbie has no time limit. At the Professional level a polar system is changed from shot to shot.
At the Demonstration mode you can`t change the Distance and the Angle, but if you press the Fire button they are showed on the radar.