Perhaps people can view some sort of "recipe" book. In which combinations are still hidden and they can unlock as soon as they find a viable combination. The silhouettes of the hidden particles could give the player a hint on which particles they would need to combine and unlocking particle combinations visualizes them in the book, making more locked combinations available. That way you keep the awesome free spirit of your current style, but give the player an option to "find" the right path when needed.