Little C extension - explanation

#include<stdio.h>

#define MAXSIZE 20
volatile char counterarray[MAXSIZE] = {0};

#define MAXDEPTH 10
int depth=0;
int olddepth=0;
int searcher=0;
int searchermax[MAXDEPTH];
int counter[MAXDEPTH];
int lastloop;
#define _ counter[depth]
#define times [counterarray]=1; \
              depth++; \
              searcher = 0;\
              for(searcher=-1; counterarray[searcher]==0; ++searcher){ \
                  searchermax[depth]=searcher+1; \
              } \
              counterarray[searcher] = 0; \
              for(counter[depth]=0; \
                      olddepth=depth, \
                      (lastloop=!!(counter[olddepth]<searchermax[olddepth])), \
                      counter[olddepth]==searchermax[olddepth]?depth--:1, \
                      olddepth = depth, \
                      lastloop; \
                      _=counter[olddepth]++)

#define NEWLINE printf("\n")
int main(int argc, char** argv){
    printf("3 times hello:\n");
    3 times printf("Hello.\n");

    NEWLINE;
    printf("Now a simple football match simulation:\n");
    3 times printf("Score: 0 : %d\n", _);

    NEWLINE;
    printf("Nested tests\n");
    2 times {
        printf("Counting: ");
        9 times {
            printf("%d ", _);
        }
        printf("\n");
    }

    NEWLINE;
    5 times {
        printf("Counting up to %d: ", _);
        _ times {
            printf("%d ", _);
        }
        printf("\n");
    }

    NEWLINE;
    printf("Some identity matrices:\n");
    7 times {
        printf("Dimension %d\n", _);
        int n = _;
        n times {
            int outer = _;
            n times {
                printf("%c ", (_==outer?'1':'0'));
            }
            printf("\n");
        }
    }

    return 0;
}