#ifndef GRAVITY_H_INCLUDED
#define GRAVITY_H_INCLUDED

#include "balls.h"

extern void gravity_constant_field (double x, double y);
extern void gravity_newton_field (double r, double g);

extern vec2d gravity_vector (const ball * b);

extern void gravity_draw_visible_field (cairo_t * cr);

extern void gravity_draw (cairo_t * cr);
extern void gravity_change (double dx, double dy);

extern void gravity_collisions (ball * begin, ball * end);

#endif