--star.lua
--code by [GB]Siapran
--15.02.2013

function drawstar(x,y,z) --draws the stars on buffer_1 with clipping
 if(x<132)and(x>0)and(y<68)and(y>0)then
  for(i=x-(8/z),x+(8/z),1)do
   for(j=y-(8/z),y+(8/z),1)do
    if (i<=128)and(i>=0)and(j<=64)and(j>=0)then
     nbdraw.pixel(i+1,j+1,0,1)
    end
   end
  end
 end
end

for(a=1,4,1)do --adjust contrast
 misc.contrast(-1)
end

clear nil

for(a=1,64,1)do --black screen in buffer_2
 nbdraw.line(1,a,128,a,2)
end

starlistx={} --global values for 3D positions
starlisty={}
starlistz={}

for(a=1,16,1)do --generate first stars (16)
 starlistx[a]=misc.random(101)-50
 starlisty[a]=misc.random(101)-50
 starlistz[a]=a*5
end


repeat --main loop

 nbdraw.copypage(2,1) --recall a black screen from buffer_2

 for(a=1,16,1)do --draw stars
  drawstar(starlistx[a]/(starlistz[a]/10)+64,starlisty[a]/(starlistz[a]/10)+32,starlist[a]/2)
 end

 for(a=1,16,1)do --move stars towards camera
  starlistz[a]=starlistz[a]-1
  if(starlistz[a]==2)then --regen if selected star is too close
   starlistx[a]=misc.random(101)-50
   starlisty[a]=misc.random(101)-50
   starlistz[a]=starlistz[a]+80
  end
 end
 
 nbdraw.copypage(1,0) --copy buffer_1 on screen

until key(0) --wait until a key is pressed