#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>
#include "util.h"
typedef struct {
  SDL_Window* w;
  SDL_Renderer* r;
} bw;
#define sdl_clear(r) SDL_SetRenderDrawColor(r,0,0,0,0);\
    SDL_RenderClear(r);
bw sdl_init();
void sdl_loop(bw);
void sdl_circle(bw w,int x, int y, int r);