// helper function: sets the vector to random direction and length
function vec_randomize (VECTOR* vec, var range)
{
   vec_set(vec,vector(random(1)-0.5,random(1)-0.5,random(1)-0.5));
   vec_normalize(vec,random(range));
}

// helper function: fades out a particle
function p_alphafade(PARTICLE *p)
{
    p.alpha -= p.skill_a*time_step;
    if (p.alpha <= 0) p.lifespan = 0;
}

function p_fountain(PARTICLE* p)
{
   VECTOR vTemp;
   vec_randomize(vTemp,2);
   vec_add(p.vel_x,vTemp);
   vec_set(p.blue,vector(random(255),random(255),255));
   set(p, MOVE | BRIGHT | TRANSLUCENT);
   p.alpha = 100;
   p.size = 2;
   p.gravity = 0.2;
   p.skill_a = 3; // fade factor
   p.event = p_alphafade;
}

function main()
{
  level_load(NULL);
  video_window(NULL,NULL,0,"Particle demo");
  vec_set(camera.x,vector(-150,0,50));
  vec_set(sky_color,vector(50,0,0)); // dark blue

  while(1)
  {
     effect(p_fountain,maxv(1,40*time_step),vector(0,0,0),vector(0,0,5));
     wait(1);
  }
}