for(int i=1; i <= MissileCount; i++) {
  Missile[i].pos.x += Missile[i].vel.x * deltatime;
  Missile[i].pos.y += Missile[i].vel.y * deltatime;
  Missile[i].life -= deltatime;
  if(Missile[i].life < 0) Missile[i].dead = true;
}