A girl with complete foresight but no recollection of the past receives a love-letter from beyond the end of her future. Guided by her friend the mathemagician, she begins a journey through the events which his calculations have predicted and her intuition has foreseen, towards the source of the curious letter.
Each instalment contains three puzzles -- usually one riddle, one number problem and one tricky puzzle -- whose answers themselves form an overall puzzle, which can only be solved when the whole of Planetarium has been completed.
I plan to check it out. This is the exact sort of game/story I'd love to write.