donut2

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define R(mul, shift, x, y) \
_= x; \
x -= mul * y >> shift; \
y += mul*_ >> shift; \
_ = 3145728 - x * x - y * y >> 11; \
x = x *_ >> 10; \
y = y *_ >> 10;

int8_t b[1760], z[1760];

void main() {

    int sA = 1024, cA = 0,sB = 1024,cB = 0, _;
    for (;;) {

        memset(b, 32, 1760);  // text buffer
        memset(z, 127, 1760);   // z buffer

        int sj = 0, cj = 1024;

        for (int j = 0; j < 90; j++) {

            int si = 0, ci = 1024;  // sine and cosine of angle i

            for (int i = 0; i < 324; i++) {
                int R1 = 1, R2 = 2048, K2 = 5120 * 1024;

                int x0 = R1 * cj + R2,
                    x1 = ci * x0 >> 10,
                    x2 = cA * sj >> 10,
                    x3 = si * x0 >> 10,
                    x4 = R1 * x2 - (sA * x3 >> 10),
                    x5 = sA * sj >> 10,
                    x6 = K2 + R1 * 1024 * x5 + cA * x3,
                    x7 = cj * si >> 10,
                    x = 40 + 30*(cB * x1 - sB * x4) / x6,
                    y = 12 + 15 * (cB * x4 + sB * x1) / x6,
                    N = (-cA * x7 - cB * ((-sA * x7 >> 10) + x2) - ci * (cj * sB >> 10) >> 10) - x5 >> 7;

                int o = x + 80 * y;
                int8_t zz = (x6 - K2) >> 15;
                if (22 > y && y > 0 && x > 0 && 80 > x && zz < z[o]){

                    z[o] = zz;

                    b[o] = ".,-~:;=!*#$@"[N > 0 ? N : 0];
                }

                R(5, 8, ci, si)  // rotate i
            }

            R(9, 7, cj, sj)  // rotate j

        }

        for (int k = 0; 1761 > k; k++){

            putchar(k % 80 ? b[k] : 10);
        }

        R(5, 7, cA, sA);
        R(5, 8, cB, sB);
        usleep(15000);
        printf("\x1b[23A");
    }
}