My concepts:
1. Ordinary and advanced option in music (which i explained in one of my decks)
2. text font modification in rules and lua:
expression in rules: change text font to ""
expression in lua:
castle.modifyText(function()
actor.textContent = ""
castle.changeFont(actor).fontName
...
end) (all text API lives in this functions otherwise castle would call it as nil if not nested in that function)
3. Advanced castle.draw modifications (like love2D)
Tell me if ts sucks or peak, thats my only concepts