Thank you so much for the video review. It's such helpful feedback. I clearly needed to provide a lot more messages to the player, eg you can't build a room inside another room and mines can only be dropped outside of the rooms/subs, there's no oxygen or light meter on easy/sandbox mode. The crashes are unfortunate. I spent so much of the time I had packing in features and polishing, I didn't have enough time to find and eliminate crash bugs.