Estimate pi by shooting arrows at a shield

pi.c

/* Estimate pi by shooting arrows at a shield.
 * https://www.smbc-comics.com/comic/math-and-war
 * Only uses integer operations except for displaying the quotient.
 */
#include <time.h>
#include <stdio.h>
#include <inttypes.h>

#define HALF    UINT64_C(0x80000000)
#define QUARTER UINT64_C(0x40000000)

static uint64_t
xoroshiro128plus(uint64_t s[2])
{
    uint64_t s0 = s[0];
    uint64_t s1 = s[1];
    uint64_t result = s0 + s1;
    s1 ^= s0;
    s[0] = ((s0 << 24) | (s0 >> 40)) ^ s1 ^ (s1 << 16);
    s[1] = (s1 << 37) | (s1 >> 27);
    return result;
}

int
main(void)
{
    uint64_t s[] = {0x8ecdf50ac9ce517d, 0xa687a3079cb1d1d2};
    uint64_t inside = 0;
    s[0] ^= time(0);
    for (uint64_t i = 1; i < UINT64_MAX; i++) {
        uint64_t r = xoroshiro128plus(s);
        uint64_t x = r & UINT64_C(0xffffffff);
        uint64_t y = r >> 32;
        if (x < HALF && y < HALF) {
            uint64_t dx = x < QUARTER ? QUARTER - x : x - QUARTER;
            uint64_t dy = y < QUARTER ? QUARTER - y : y - QUARTER;
            if (dx * dx + dy * dy < UINT64_C(0x1000000000000000))
                inside++;
        }
        if (!(i & UINT64_C(0x3ffffff))) {
            printf("%.17g %" PRIu64 " %" PRIu64 "\n",
                   16.0 * inside / i, 16 * inside, i);
            fflush(stdout);
        }
    }
}