snowflake

#include <stdlib.h>     // abs
#include <iomanip>
#include <iostream>
using   std::setw,
        std::cout, std::endl;

auto main()
    -> int
{
    const int n = 4;
    const int w = 1 << n;
    for( int y = 0; y < 2*w - 1; ++y ) {
        const int cw = w - 1;
        cout << setw( abs( cw - y ) ) << "";
        const int cy = cw - abs( cw - y );
        for( int x = 0; x < w + y; ++x ) {
            const int tx = (x < cy? x : x < w? w - 1 - x : x + 1 - w);
            const int ty = (x < cy? cy : x < w? w - 1 - cy : cy);
            const char ch = (tx & ~ty? ' ' : '@');
            cout << setw( 2 ) << ch;
        }
        cout << endl;
    }
}