#include<time.h>
#include<stdlib.h>
#include"SDL.h"

#define A 64
#define B 256

#define Z(a, b, c) a ## b ## c

typedef Sint32 i;
i p[A][4][B][2], d[4][B][2], q = 0, b[4][2],
S, C, H, I, e, R, K, E = 1,
w = 800, h = 600,
G, u, t, s = SDL_HWSURFACE|SDL_DOUBLEBUF,
P[4][3] =
{
   {255, 16, 16},
   {0, 255, 0},
   {255, 255, 64},
   {64, 128, 255}
};

SDL_Event n;
const SDL_VideoInfo *v;
SDL_Surface *o;

i O(i x, i y)
{
   return (y - x) * (float)rand() / RAND_MAX + x;
}

void g(i z, i x, i y)
{
   if( p[q][I][S][C] < z )
      d[I][S][C] += O(x, y);
   if( p[q][I][S][C] > z )
      d[I][S][C] -= O(x, y);
   e = d[I][S][C];
   d[I][S][C] = e < -H ? -H : (e > H ? H : e);
}

void c(i x, i y, i z)
{
   t = SDL_MapRGB(o->format, x * S / A, y * S / A, z * S / A);
}

#define r(type) \
{                                                                            \
   for(S = 1; S <= A; S++)                                                   \
   {                                                                         \
      C = (q + S) % A;                                                       \
      for(I = 0; I < 4; I++)                                                 \
      {                                                                      \
         c(255, 255, 255);                                                   \
         for(H = 0; H < B; H++)                                              \
         {                                                                   \
            if( H == 1 )                                                     \
               c(P[I][0], P[I][1], P[I][2]);                                 \
                                                                             \
            e = p[C][I][H][0];                                               \
            e >>= 16;                                                        \
            if( e >= 0 && e < w )                                            \
            {                                                                \
               R = p[C][I][H][1];                                            \
               R >>= 16;                                                     \
               if( R >= 0 && R < h )                                         \
                  *(type*)((Uint8*)(o->pixels) +                             \
                                    R * o->pitch +                           \
                                    e * K)                                   \
                     = (type)t;                                              \
            }                                                                \
         }                                                                   \
      }                                                                      \
   }                                                                         \
}

int main(int x, char **y)
{
   if( SDL_Init(SDL_INIT_VIDEO) < 0 )
      puts("Unable to init SDL");
   else
   {
      atexit(SDL_Quit);

      v = SDL_GetVideoInfo();
      K = v->vfmt->BytesPerPixel;
      if( K - 2 && K - 4 )
         puts("Unsupported pixel format");
      else
      {
         if( x > 1 )
            s |= SDL_FULLSCREEN;
         o = SDL_SetVideoMode(w, h, K * 8, s);
         if( o == NULL )
            puts("Error initializing screen");
         else
         {
            SDL_WM_SetCaption("Schierke", NULL);
            SDL_ShowCursor(SDL_DISABLE);

            srand(time(NULL));

            for(I = 0; I < 4; I++)
            {
               for(S = 0; S < B; S++)
               {
                  p[0][I][S][0] = O(0, w << 16);
                  for(p[C = 0][I][S][1] = O(0, h << 16);
                      C < 2;
                      d[I][S][C++] = O(-3 << 16, 3 << 16));
               }
               for(S = 1; S < A; S++)
                  for(C = 0; C < B; C++)
                     for(H = 0; H < 2; H++)
                        p[S][I][C][H] = p[0][I][C][H];
               b[I][0] = O(0, w << 16);
               b[I][1] = O(0, h << 16);
            }

            for(u = SDL_GetTicks();
                E;)
            {
               u += 16;

               c(0, 0, 0);
               SDL_LockSurface(o);
               SDL_FillRect(o, NULL, t);
               if( o->format->BytesPerPixel == 4 )
                  r(Uint32)
               else
                  r(Uint16)
               SDL_UnlockSurface(o);
               SDL_Flip(o);

               for(I = 0; I < 4; I++)
               {
                  if( !O(0, 60) )
                  {
                     b[I][0] = O(50 << 16, (w - 50) << 16);
                     b[I][1] = O(50 << 16, (h - 50) << 16);
                  }
                  H = 2 << 16;
                  g(b[I][S = C = 0], 16, 1 << 12);
                  g(b[I][C = 1], 16, 1 << 12);

                  H *= 2;
                  for(S = 1; S < B; S++)
                  {
                     g(p[q][I][0][C = 0], 32, 3 << 11);
                     g(p[q][I][0][C = 1], 32, 3 << 11);
                  }

                  H = (q + 1) % A;
                  for(S = 0; S < B; S++)
                     for(C = 0; C < 2; C++)
                        p[H][I][S][C] = p[q][I][S][C] + d[I][S][C];
               }
               for (q = H; SDL_PollEvent(&n);)
                  if( n.type == SDL_KEYDOWN || n.type == SDL_QUIT )
                     E = 0;

               G = SDL_GetTicks();
               if( G < u )
                  SDL_Delay(u - G);
            }

            SDL_FreeSurface(o);
         }
      }
      SDL_Quit();
   }
   return 0;
}