A more readable version

2048.c

M[16],X=16,W,k;

main(){
    T(system("stty cbreak"));
    puts(W&1?"WIN":"LOSE");
}
K[]={2,3,1};
s(f,d,i,j,l,P){
    for(i=4;i--;){
        for(j=k=l=0;k<4;){
           j<4?P=M[w(d,i,j++)],W|=P>>11,l*P&&(f?M[w(d,i,k)]=l<<(l==P):0,k++),l=l?P?l-P?P:0:l:P:(f?M[w(d,i,k)]=l:0,++k,W|=2*!l,l=0);
        }
    }
}

w(d,i,j){
    return d?w(d-1,j,3-i):4*i+j;
}
T(i){
  for(i=X+rand()%X;M[i%X]*i;i--)
      ;
  i?M[i%X]=2<<rand()%2:0;
    for(W=i=0;i<4;)
      s(0,i++);
      for(i=X,puts("\e[2J\e[H");i--;i%4||puts(""))
       printf(M[i]?"%4d|":"    |",M[i]);
       W-2||read(0,&k,3)|T(s (1,K[(k>>X)%4]));
}//[2048]