"Event Horizon" in one equation

main.c

// https://x.com/tsoding/status/1897049953090068614/photo/1
//cc -o main main.c -lm && ./main
#include <stdio.h>
#include <math.h>

#define WIDTH 30
#define HEIGHT 30

int main() {
    float w = WIDTH;
    float h = HEIGHT;
    for (int col=0; col < HEIGHT; ++col){
        for (int row=0; row < WIDTH; ++row) {
            float x = col;
            float y = row;
            float cx=(2*x-w)/h;
            float cy=(2*y-h)/h;
            float d=sqrtf(cx*cx+cy*cy);;
            d-=0.5;
            d+=0.01*h/(2*(x-y)+h-w);
            d= fabsf(d);
            d=0.1/d;
            char c="-+=<@#"[(int)floorf(d/(1+d)*7)];
            printf("%c%c",c,c);

        }
        printf("\n");
    }
    return 0;

}