Linux version (possibly cross-platform) of circle illusion

// Original by https://codegolf.stackexchange.com/users/21158/fabricio
// https://codegolf.stackexchange.com/questions/34887/make-a-circle-illusion-animation?newreg=6661e4328c904030a57b9f7646a65278

#include <stdio.h>
#include <stdlib.h>
#include <cmath>

// thanks to http://www.cplusplus.com/forum/unices/10491/
#if defined(__WIN32__) || defined(_WIN32) || defined(WIN32) || defined(__WINDOWS__) || defined(__TOS_WIN__)

  #include <windows.h>

  inline void delay( unsigned long ms )
    {
    Sleep( ms );
    }

#else  /* presume POSIX */

  #include <unistd.h>

  inline void delay( unsigned long ms )
    {
    usleep( ms * 1000 );
    }

#endif

int round_unique (double r) { return (r > 0.0) ? (r + 0.5) : (r - 0.5); }
void print (char * buffer, int x, int y, int w, int h, char c) {
    if(x < w && y < h)
        buffer[y*w+x] = c;
}

void flush(char * buffer, int w, int h) {
    for(int y = 0; y < h; y++) {
        for(int x = 0; x < w; x++) {
            printf("%c", buffer[y*w+x]);
        }

        printf("\n");
    }
}

void clear(char * buffer, int len) {
    for(int i = 0; i < len; i++) {
        buffer[i] = ' ';
    }
}

int main ()
{
    float pi = 3.14159265358979323846;
    float circle = pi * 2;
    int len = 12;
    int hlen = len / 2;
    int cx = 13;
    int cy = 8;
    float w = 11.0;
    float h =  8.0;
    float step = 0.0;

    int W = 30;
    int H = 20;

    char buffer[W*H];



    while (1)
    {
        clear(buffer, W*H);
        for (int i = 0; i < len; i++)
        {

            float a = (i / (float)len) * circle;
            int x = cx + round_unique(cos(a) * w);
            int y = cy + round_unique(sin(a) * h);
            print(buffer, x, y, W, H, 'O');

            if (i < hlen) continue;

            step -= 0.05;
            float range = cos(a + step);
            x = cx + round_unique(cos(a) * (w - 1) * range);
            y = cy + round_unique(sin(a) * (h - 1) * range);
            print(buffer, x, y, W, H, 'O');
        }

        flush(buffer, W, H);
        delay(100);
    }

    return 0;
}