Thanks for playing, good to hear how much you enjoyed it :)
Sounds like you found the super special secret level - nah, that shouldn't be possible as the tiles around the outer edge shouldn't be removable or even considered during level generation, so there's a bug in there somewhere, I've not seen it happen before so well found!
Post voting I intend to make it so that the player can see the level seed, which would make it easier for me to recreate bugs like this.