chess board

patches-own[ 
living? live-neighbors
]

to setup 
clear-all
ask patches[
  ifelse remainder (pxcor + pycor)2 = 0
  [cell-birth]
  [cell-death] 
]
reset-ticks 
end 

to cell-birth
set living? true
set pcolor red
end 

to cell-death
set living? false
set pcolor black  
end 

to go 
ask patches[
set live-neighbors count neighbors with [living? = true]
]
ask patches with [living? = true] 
[ if live-neighbors < 2 or live-neighbors > 3 [cell-death]
]
ask patches with [living? = false]
[if live-neighbors = 3 [cell-birth]
]
tick
end