Paintball Simulation

paintball.r

# Simulation of a Paintball Game.
# The two players start off in random positions. They move one square each turn. Then they shoot at each other.
# Probability of who shoots first is 50/50. 
# Probability of a hit is proportional to the distance between the players.
# Tracks history of last 3 moves.
# Prints out graphs to show the movement of the players and the shots.
# Game over when someone is hit.

shoot<-function(a.pos,b.pos){
  # returns TRUE if the shot was a hit, otherwise FALSE
  distance<-sqrt(sum(a.pos * b.pos))
  shot.prob<-1/distance
  u<-runif(1)
  if(shot.prob > u){
    return(TRUE)
  }
  else{
    return(FALSE)
  }
}
move<-function(pos){
  # pos is a 2-vector showing the position. Returns the new position.
  direction=c(0,0)
  while(direction[1] == 0 && direction[2] == 0){
    direction<-sample(c(-1,0,1),2,replace=TRUE)
  }
  if(pos[1]==1 && direction[1]== -1){
    direction[1]= 1
  } else if(pos[1]==10 && direction[1]==1){
    direction[1]= -1
  }
  if(pos[2]==1 && direction[2]== -1){
    direction[2] = 1
  } else if(pos[2]==10 && direction[2] == 1){
    direction[2] = -1
  }
  return(pos+direction)
}
plot.moves<-function(a,b,t){
  plot(a,type='l',xlim=c(0,11),ylim=c(0,11),main=paste("Turn",t),xlab='',ylab='',col='red',lwd=2)
  points(a[3,1],a[3,2],pch='A',cex=2,col='red')
  lines(b,col='blue',lwd=2)
  points(b[3,1],b[3,2],pch='B',cex=2,col='blue')
}
paintball<-function(player1="A",player2="B"){
  players<-c(player1,player2)
  run<-TRUE
  t<-0
  a<-matrix(NA,3,2)
  b<-matrix(NA,3,2)
  a[2,]<-a[3,]<-a[1,]<-sample(10,2)
  b[2,]<-b[3,]<-b[1,]<-sample(10,2)
  while(run){
    # keep track of history
    t<-t+1
    a[c(1,2),]<-a[c(2,3),]
    b[c(1,2),]<-b[c(2,3),]
    # move players
    a[3,]<-move(a[3,])
    b[3,]<-move(b[3,])
    plot.moves(a,b,t)
    Sys.sleep(1)
    # determine which shots are hits/misses
    a.fire<-shoot(a[3,],b[3,])
    b.fire<-shoot(a[3,],b[3,])
    #establish who shoots first
    first<-sample(players,1)
    if(first==players[1]){ 
      p1<-a; col1<-'red'; p2<-b; col2<-'blue'
      p1.fire<-a.fire; p2.fire<-b.fire
    } else{
      p1<-b; col1<-'blue'; p2<-a; col2<-'red'
      p1.fire<-b.fire; p2.fire<-a.fire
    }
    traj<-rbind(a[3,],b[3,])
    if(p1.fire){ #case where first shot was a hit
      lines(traj,lty=1,col=col1,lwd=2)
      winner=first
      run=FALSE
    } else { #first shot was a miss
      lines(traj,lty=2,col=col1,lwd=2)
      Sys.sleep(1)
      if(p2.fire){ #second shot was a hit
        lines(traj,lty=1,col=col2,lwd=2)
        winner=players[players!=first]
        run=FALSE
      } else { # second shot was a miss
        lines(traj,lty=2,col=col2,lwd=2)
      }
    }
    Sys.sleep(2)
  }
  print(paste("The Winner was:",winner))
}

paintball()