I had time to do a full play through recently which lead me to update to version 4.1. It took me just over 10 hours to do everything there is to do.
I added a few more puzzles, made a few things easier and a few things harder. I found several bugs which are now corrected.
If you see a version on the title screen of the game earlier than 4.1 you can transfer your save files (named Save1-4.rvdata in the game directory) to the new version by dragging and dropping them into the newly downloaded directory.
It's been a year since I finished Knight's Dungeon so I'm starting a new series of 5 side-quests that will take about 30 min to an hour of play time each. 3 out of 5 of the side-quests are now included in the regular download. I've also thrown in some new music so now every level has its own. I'll be taking a break now to decide what the other 2 side-quests will be!