rainbow.r

library(nara)
library(grid)

x11(type = 'dbcairo', antialias = 'none', width = 8, height = 6)
dev.control('inhibit')
w<-400
h<-300
nr <- nr_new(w, h, 'black')

l1 <- c(floor(runif(1,0,w)),floor(runif(1,0,h)))
l2 <- c(floor(runif(1,0,w)),floor(runif(1,0,h)))
d1 <- c(runif(2,-2,2))
d2 <- c(runif(2,-2,2))

cvec<-c("red","orange","yellow","green","blue","purple")

rvec <- matrix(NA,nrow=100,ncol=4)
rvi <- 1
for(i in 1:100000){
  
  if(i>98){
    nr_line(nr,rvec[rvi,1],rvec[rvi,2],rvec[rvi,3],rvec[rvi,4],"black")
  }
  
  
  selcol <- cvec[(i %% length(cvec))+1]
  nr_line(nr,l1[1],l1[2],l2[1],l2[2],selcol)
  
  if(l1[1] > w | l1[1] <=0){d1[1]=-d1[1]}
  if(l1[2] > h | l1[2] <=0){d1[2]=-d1[2]}
  
  if(l2[1] > w | l2[1] <=0){d2[1]=-d2[1]}
  if(l2[2] > h | l2[2] <=0){d2[2]=-d2[2]}
  
  l1 <- l1 + d1
  l2 <- l2 + d2
  
  rvec[rvi,] <- c(l1[1],l1[2],l2[1],l2[2])
  rvi <- rvi + 1
  if(rvi == 100){
    rvi <- 1
  }
  
  dev.hold()
  grid.raster(nr, interpolate = FALSE)
  dev.flush()
  Sys.sleep(0.01)
}