ParatimParatim is the abbreviation of Paratrooper improved.
The game is based on the old Paratrooper game by Orion Software. It can be downloaded for free from several abandonware sites.
The current version of Paratim is playable, but there isn't much improved compared to the old DOS game. This is planned for later releases however.
In the game you play with the gun in the bottom center of the game while helicopters fly overhead. Those helicopters sometimes drop paratroopers. When their are four or more paratroopers on one side of the gun it's game over. To prevent this you have to shoot the paratroopers while they fall and/or the helicopters.
After a round of helicopters planes arrive that drop bombs aimed at the gun. If a bomb hits you it's game over as well. To prevent this you have to shoot the bomb and/or the airplanes.
The controls of the game are very simple:
Point gun left/right: Arrow key left/right
Fire bullet: Arrow key up