space-warrior-chapter-9.cpp

bool OnUserUpdate(float fElapsedTime) override
{
  Clear(olc::BLACK);
  DrawSprite(fPlayerPositionX, fPlayerPositionY, sprPlayer.get());
  if (GetKey(olc::Key::LEFT).bHeld) {
    fPlayerPositionX = fPlayerPositionX - fPlayerVel * fElapsedTime;
   }
  if (GetKey(olc::Key::RIGHT).bHeld) {
    fPlayerPositionX = fPlayerPositionX + fPlayerVel * fElapsedTime;
    }
  if (GetKey(olc::Key::UP).bHeld) {
    fPlayerPositionY = fPlayerPositionY - fPlayerVel * fElapsedTime;
   }
  if (GetKey(olc::Key::DOWN).bHeld) {
      fPlayerPositionY = fPlayerPositionY + fPlayerVel * fElapsedTime;
    }
  if (GetKey(olc::Key::SPACE).bPressed) {
       float ftempX = fPlayerPositionX;
       float ftempY = fPlayerPositionY;
       vBullet.emplace_back(Bullet{ftempX + float(sprPlayer->width) / 2, ftempY, false});
      }

   for (auto elm: vEnemy) {
      if (elm.alive)
        DrawSprite(elm.x, elm.y, sprEnemy.get());
    }

    for (auto &elm: vBullet) {
        // only take care of bullets which are visible on the screen
        if (elm.y > -1 && !elm.dead) {
            FillCircle(int(elm.x), int(elm.y), 1, olc::RED);
            elm.y = elm.y - fBulletVel * fElapsedTime;
        }
    }

    for (auto &elm: vBullet)
     {
       for (auto &enemy: vEnemy)
        {
        if (!elm.dead && enemy.alive && elm.y > enemy.y && elm.x + 1 >= enemy.x &&
            elm.x - 1 <= enemy.x + float(sprEnemy->width) &&
             elm.y - 1 <= enemy.y + float(sprEnemy->height)) 
            {
               // kill both bullet and enemy.
                  elm.dead = true;
                  enemy.alive = false;
              }
           }
        }

   for(auto &elm : vEnemy){
    if(elm.alive){
        float tempX = ((fPlayerPositionX + float(sprPlayer->width) / 2
         ) - elm.x + float(sprEnemy->height) + float(sprEnemy->width) / 2
                               );
        float tempY = (fPlayerPositionY - elm.y + float(sprEnemy->height));

        // simple pythagoras theorem
        float tempHypo = powf(tempX, 2) + powf(tempY, 2);
        float Hypo = sqrtf(tempHypo);

        float sinTheta = (tempY / Hypo);
        float cosTheta = (tempX / Hypo);

        elm.x = elm.x + fEnemyVel * cosTheta * fElapsedTime;
        elm.y = elm.y + fEnemyVel * sinTheta * fElapsedTime;

        if (elm.x + sprEnemy->width >= fPlayerPositionX &&
            elm.x <= fPlayerPositionX + sprPlayer->width &&
            elm.y + sprEnemy->height >= fPlayerPositionY)
        {
          elm.alive = false;
        }
          break;
     }
   }

return true;
}