So i got some sleep and i think i have the general idea for the layout done:

Brains tend to be kinda limited on what they can remember - so i thought why not make a game from that. Organize your brain in your daily live, collect memories and use them to interact with people, attend events and ace your tests at school. Try not to forget your friends names, the dates of events and try to ace your tests - otherwise your brain will shrink! If you remembered something long enough it gets transferred into your endlessly big long term brain, that way it will no longer need space in your limited short term brain.

You will play round based thru your days to use and collect memories, at night u can recall memories from or write them into your diary or you decide to sleep over them to slowly get them into your long term brain.

I hope i will be able to create a fun and challenging game with that idea, gonna start coding now! :>