: mmap ( m quot -- m' ) '[ _ map ] map ; inline
: 2mmap ( m m2 quot -- m' ) '[ _ 2map ] 2map ; inline

: aggregate ( v -- v' )
    dup dup <reversed> [ unclip drop f suffix ] bi@ <reversed>
    [ 2array ] 2map [ swap prefix ] 2map [ sift ] map ;
    
: neighbours ( m -- m ) 
    [ aggregate ] map flip [ aggregate ] map [ concat ] mmap ;
    
SYMBOLS: on off dying ;
    
: step-cell ( state neighbours -- state' )
    [ on = ] filter length swap
    {
        { on [ drop dying ] }
        { dying [ drop off ] }
        { off [ 2 = [ on ] [ off ] if ] }
    } case ;
        
: random-world ( xy -- m ) 
    first2 zero-matrix 
    [ drop { on off dying } random ] mmap ;
    
: step-world ( m -- m' ) dup neighbours [ step-cell ] 2mmap ;