typedef struct QB QB;

typedef struct QB QB;
typedef struct Body Body;
typedef struct Quad Quad;
typedef struct Vector Vector;

struct QB {
union {
Quad *q;
Body *b;
};
int t;
};

struct Vector {
double x, y;
};

struct Body {
Vector;
Vector v, a, newa;
double size, mass;
Image *col;
};

struct Quad {
Vector;
QB c[4];
double mass;
};

#pragma varargck type "B" Body*

struct {
QLock;
Body *a;
int nb, max;
} glxy;

struct {
Quad *a;
int l, max;
} quads;

#define π2 6.28318530718e0

enum {
EMPTY,
QUAD,
BODY,
};

void quit(char*);

Image *randcol(void);
Point topoint(Vector);
Vector tovector(Point);

Body *body(void);
void drawbody(Body*);
Vector center(void);
void glxyinit(void);
int Bfmt(Fmt*);
void readglxy(int);
void writeglxy(int);
void drawglxy(void);

void simulate(void*);

void quadcalc(Body*, QB, double);
int quadins(Body*, double);
void growquads(void);
void quadsinit(void);

int stats, quaddepth, calcs, extraproc, throttle;
double G, θ, scale, ε, LIM, dt, dt², avgcalcs;
Point orig;
QB space;
Body ZB;

enum {
STK = 8192,
};

#define STATS(e) if(stats) {e}

#define CHECKLIM(b, f) \
if(((f) = fabs((b)->x)) > LIM/2) \
LIM = (f)*2; \
if(((f) = fabs((b)->y)) > LIM/2) \
LIM = (f)*2