main.cpp

#include <chrono>
#include <thread>
#include <cstdlib>
#include <math.h>
#include "render.cpp"

#define PI 3.14159265

int main() {
  int i = 0;
  render::init();
  std::atexit(render::on_exit);
  while (true) {
    ++i;
    render::render(static_cast<int>(1500.0 + 300.5 * pow(abs(sin(i / 500.0 * PI)), 5)));
    std::this_thread::sleep_for(std::chrono::milliseconds(1000/60));
  }

  return 0;
}

render.cpp

#include <iostream>
#include <vector>

namespace render {
  const int w = 200;
  const int h = 65;
  std::string buffer = "";
  void write(std::string text) {
    buffer += text;
    //std::cout << text << std::flush;
  }
  void write(std::vector<std::string> text) {
    for(const auto& part : text) {
      //std::cout << part;
      buffer += part;
    }
    //std::cout << std::flush;
  }
  void writeln(std::string text) {
    if (text.length() >= w) {
      buffer += text.substr(0, w) + "\n";
    } else {
      buffer += text + std::string(w - text.length(), ' ') + "\n";
    }
  }
  void flush() {
    std::cout << buffer << std::flush;
    buffer.clear();
  }
  void pos(int x, int y) {
    std::string sx = std::to_string(x);
    std::string sy = std::to_string(y);
    write({ "\e[", sy, ";", sx, "H" });
  }
  void clear() {
    //pos(h, 0);
    //write(std::string(h, '\n'));
    pos(0, 0);
  }
  int max(int a, int b) {
    return a > b ? a : b;
  }
  void render(int i) {
    clear();
    char chars[] = { '.', ':', '+', 'o', 'O', '@'};
    int charCount = 6;
    //write({ "hi ", std::to_string(i), "\n" });
    for(int j = i; j > (i - h) && j > 0; --j) {
      int n = j * 3;
      int size = max((n/w % 2) == 0 ? n % w : w - (n % w), 3);
      int offset = abs(j * j&(j+3) + j%i) % 8;
      const char letter = chars[((j/(charCount-1)) % 2) == 0 ? j % 5 : 5 - (j % 5)];
      writeln(std::to_string(j) + " - " + std::string(w/2 - size/2 + offset, ' ') + std::string(size, letter));
    }
    flush();
  }
  void init() {
    // smcup
    write("\e[?1049h");
  }
  void on_exit() {
    // rmcup
    write("\e[?10491");
  }
}