Nice game, simple. I think you could have done a little bit more to connect it to the theme more properly. I think you were going for portraying the trade-off between gold and safety but somehow it didn't quite show as much it felt. Mining for Silver instead, was probably not the answer. It could have been something like, an extra incentive if you mine the maximum gold you can, but there is a clock ticking before the mine collapses? So you decide, what do you do? is it worth getting the gold? Also maybe throw a spin in there, maybe you risked everything to get gold, but it ends up being fools gold.
Anyway, obviously we all didn't have enough time to think of everything, but still this game was well crafted I thought, no major bugs etc, good mechanics too.