moonphase.c

#include <time.h>
#include <stdio.h>

        int main(
     ){int x=-   44,
   a=2551443,b=-    x,
  y=2-b,z=(time(0     )
 -592531)%a*512/a      ;
 for(;y<=b;putchar     (
 ++x>=a?x=-b,y+=4,     9
 ^3:x<0?x=x*x+y*y      <
  b*b?a=1-x,-1:x+     1
   ,32:"#."[(x<a    *(
     ~z&255)>>   8)^
        z>>8]));}

It shows a view from the northern hemisphere, to see from the southern replace <a*(~ with >=a*(. Can't show a view near the equator.