A snake game in a hand full of Ruby

snake.rb

#!/usr/bin/env ruby
d,l,s,c,f,S=15,3,[[5,6],[5,5],[5,4]],[1,0],[rand(15),rand(15)],STDIN
system'stty -icanon -echoke'
loop do
  k=S.getc if k=select([S],[],[],0.2)&&S.getc=="\e"&&S.getc==?[
  c={?A=>[0,-1],?B=>[0,1],?C=>[1,0],?D=>[-1,0]}[k]||c
  s=[[s[0][0]+c[0],s[0][1]+c[1]]]+s[0..-2]
  exit if s[0][0]+1>d||s[0][1]+1>d||s[0][0]+1==0||s[0][1]+1==0||s[1..-1].index(s[0])
  s+=[[s[0][0]+c[0],s[0][1]+c[1]]] if s[0]==f
  f=[rand(d),rand(d)] if s.index f  
  (d+3).times{|y|(d+3).times{|x|print y==0?"\e[2J\e[1;1H": s.index([x-1,y-2])? ?#: f==[x-1,y-2]? ?@: x==d+2? "\n": y==1||y==d+2||x==0||x==d+1? ?X: ' '}}
end