The newest pre-alpha release (v11, 0.0.2.0) brings the feature many players who tried out the recently released demo asked for - the ability to save the progress and continue playing the game later. It works only for players who select casual/easy mode, and old school/hard gamers will still have to finish the game in one sitting (because this mode is for getting some tough achievements, if the game ever gets on Steam).
Both early access (for early supporters) and demo releases have been updated.