Spoilers, Do Not Read

I think there are a couple of things in Sandcastle Builder that should be better explained to the player.  Perhaps through the use of the Free Advice boost.  If you've been playing for a month and feel like your game is at a standstill, here is a cheat sheet.

1. Get a temporal rift.  If you already have infinite castles you can't get one of these so you can use time travel or the Navigation Code in partnership with Fireproof to create a temporary zero castle state with which to create one with a Question Qube.  A button to jump through the rift will appear in your notification log.  Jump through the rift, then click the button to jump through it again.  Trying to jump through a second rift in the same NP will unlock Time Lord.  Buy it, allowing you to jump through a second rift.  Then click that jump button one more time without generating a new rift.  The rest follows quite obviously.

2. Unrelated to (1) above, for endgame you need at least 400 goats.