A random dungeon generator that (no longer) fits on a business card

generate.c

#include <time.h> //  Robert Nystrom
#include <stdio.h> // @munificentbob
#include <stdlib.h> //     for Ginny
                     //    2008-2019

const int H = 40;
const int W = 80;
int m[H][W];

int g(int x)
{
    return rand() % x;
}

void cave(int s)
{
    int w = g(10) + 5;
    int h = g(6) + 3;
    int t = g(W - w - 2) + 1;
    int u = g(H - h - 2) + 1;
    for (int y = u - 1; y < u + h + 2; y++)
        for (int x = t - 1; x < t + w + 2; x++)
            if (m[y][x] == '.')
                return;
    int d = 0;
    int e, f;
    if (!s) {
        for (int y = u - 1; y < u + h + 2; y++)
            for (int x = t - 1; x < t + w + 2; x++) {
                int s = x < t || x > t + w;
                int t = y < u || y > u + h;
                if (s ^ t && m[y] [x] == '#') {
                    d++;
                    if (g(d) == 0)
                        e = x, f = y;
                }
            }
        if (d == 0) return;
    }
    for (int y = u - 1; y < u + h + 2; y++)
        for (int x = t - 1; x < t + w + 2; x++) {
            int s = x < t || x > t + w;
            int t = y < u || y > u + h;
            m[y][x] = s && t ? '!' : s ^ t ? '#' : '.' ;
        }
        if (d > 0)
        m[f][e] = g(2) ? '\'' : '+';
    for (int j = 0; j < (s ?  1 : g(6) + 1); j++)
        m[g(h) + u][g(w) + t] = s ? '@' : g(4) == 0 ?  '$' : 65 + g(62);
}

int main(int argc, const char *argv[]) {
    srand((int) time(NULL));
    for (int y = 0; y < H; y++)
        for (int x = 0; x < W; x++)
            m[y][x] = ' ';
    for (int j = 0; j < 1000; j++)
        cave(j == 0);
    for (int y = 0; y < H; y++)
        for (int x = 0; x < W; x++) {
            int c = m[y][x];
            putchar(c == '!' ?  '#' : c);
            if (x == W - 1)
                printf("\n");
        }
    return 0;
}