Okay so I'm pretty sure I 100%'d the game but something feels off for me. I got the final beautiful secret but it feels like there's still more to explore. For example, the empty slot for a possible 6th key? The nearly empty right side and left side of the inventory? Leftover euros? The one stray boost pad at the top left of the key-gate? Maybe it's just slightly rough, considering this is a huge game compared to the rest of his works, but maybe it's just all in my head. Nonetheless, this game is amazing with small details and clues to help you with some secrets.
(Edit: Nevermind it says I got 100% on the splash screen)