Spoilers, kinda. Just describing what happens after you find after you find all collectibles...
Or rather what doesn't happen.
Not bashing the game. I loved trying to get all of the collectables (that we know of). Other than brute forcing the Monolith puzzle, it's been a gratifying cerebral struggle the whole way.
I'm just let down that there seems to be no "true" ending after getting the last collectable. I access the 64 cube room...then I'm in a room with 3 heart cubes floating together as one big heart, and that's it. No ending sequence, no closure at all. I'm just left to turn off the game when I'm tired of waiting for something to happen.
Where's the payoff? Did I miss something? This leads me to believe that there's more to the game, and the community just hasn't found it yet. Is it possible that there are even more heart containers and it's meant to form a giant red cube? Just grasping for ideas.
If this is all there is... well I guess S-ranking the game is pretty good too. I never care enough to S-rank a game except Pac Man CE DX, which took no effort. So now I have another. Cool.