basic gameplay for cooperative

src/app/Fireworks.cpp

@@ -144,4 +144,7 @@ void draw(SDL_Renderer* renderer, SDL_Texture*) {
 
 double getLogoAnimCounter() { return logoAnimCounter; }
 int getHoveredButton() { return hoveredButton; }
+void spawn(float x, float y) {
+    fireworks.emplace_back(x, y);
+}
 } // namespace AppFireworks