I am a bit puzzled because the game is called "Vault of Seraphim", but title default selection is the old levels from Catacombs of Cherubim. I'd expect the new levels to be default choice and the old ones to be bonus.
It's also not obvious to me without reading the infosheet that this is a choice, maybe add some words on screen that it is one.
Furthermore I'd like to get back to the choice first with firebutton when title cycles though cave previews, not immediately start game.
And there is a bug I noticed: when finishing a 4th level: You don't get bonus for the gems here before hero bonus, like in the previous levels.