Game probably needs some way of making the player feel more invested in the game. Maybe you can only place so many particles per day, and then you have to wait until the next day. Or you can pay to get more particles now.

If you could pay for some bonus materials that would be great too. Though I'd rather unlock them randomly from a kind of loot box system.

And how come I can't level up? I don't feel like I'm making any progress without an XP bar. Clearly this person does not understand game design.