Info: 3D-program; Request: improve it

Greetings!

I have some problems with the edges in the 3D picture this simple program
generates. I'd appriciate if someone could give some hints how to make
them better!

	/Matti

#include <stdlib.h>
 
const int s_length = 97;
 
void main(void)
{
  char s[100];
  int j, i, e, repeat;
 
  for(e = 0; e < 7; e++)
    printf("X%15s", "");
  puts("");
 
  j = 30;
  while(j >= 0)
  {
    e = s[s_length] = i = 0;
    while(i < s_length)
    {
      if( (j < 4) || (j > 25) )
        repeat = 13;
      else
        if( (((i >= 3*repeat) && (i <= 5*repeat)) && ((j > 8) && (j < 20))) )
          repeat = 11;
        else
          if( (i < 2*repeat) || (i > 6*repeat) )
            repeat = 13;
          else
            repeat = 12;
      
      if(i < repeat)
        s[i++] = '!' + random() % 92;
      else
        s[i++] = s[i - repeat];
    }
    s[i] = '\0';
    puts(s);
    j--;
  }
}