I really like the take on this, even if I sometimes come across TNT that I swear shouldn't be there according to surrounding numbers. The upgrades though don't really do much though. Slightly increasing mining speed, and carrying capacity. Its little improvements but doesn't really help out much like most upgrades in incremental games. What about something that give you an ability to place a bomb to clear a space, or a device you can use from time to time that will confirm if TNT is in a spot that you're unsure about? Abilities you can buy that have timers so you can't just spam them. Something to give a little bit of help those of us who aren't masters at minesweeper. For example, an ability that has a 1 min timer that can confirm if a spot you're looking at has TNT or not. Upgrades to increase movement speed. There are probably other little upgrades that could be added that wouldn't take away from the challenge to much if done right.