I'm having fun so far. One thing to consider is changing it so that the board layout (under the top layer) isn't generated until your first click on the board, and making the first click on the board ALWAYS be an empty space. The original minesweeper included this feature. It prevents instant/auto loss, though I realize that the damage over time precludes this. It's still an unfun mechanic for the first button you click to give you a rat/spider/wolf chewing on you.
Also there's an obvious prograssion within a given level. I nver upgraded to level 2 for 500g, and am now getting WAY less income per run since i cant complete them since theyre suddenly so much harder than the first runs were.