STALKER - The Irish Zone
Time in combat occurs in Rounds, which roughly represent two seconds. During a round, all participants in the combat will be able to perform a certain amount of actions, such as firing a weapon, moving, reloading, applying medical aid, set up explosives, etc. The time that these actions take up varies according to the type of action, and are generally referred to as Half, Full, or Reaction actions. A player can make two Half actions (though not the same action twice), or one Full action on his or her turn. Reactions come into play when it is not the players turn.
At the beginning of each round, each participant rolls 1d20, subtracts any Speed Penalty as well as any other modifiers in effect, and determines his initiative. The participant with the highest initiative acts first, and actions proceed in descending order of initiative. Tied init scores can occur, and in such cases the participant with the highest Speed goes first, and if those tie, the participant with the lowest Speed Penalty goes first.