This is a very interesting game concept! I would love to see this ported to android as I could see it's controls being translated very easily to the mobile platform.
I found that in this build, pressing the R key re-generates the cave, but any chests you open will be empty and you then appear to be stuck.
When progressing down to another floor, any extra helpers, miners, and devices persist at the position they were in the previous floor. Perhaps making it so they disappear, or make sure the game generates enough empty space to be around 1 of the miners so it can place the extras.
I like how you can use the arrow keys to quickly move the map around. It would be nice to either have a mini-map or a feature to scroll out the map with the scroll wheel.
Something that could make this more interesting is to have a miner, and a fighter to fight off monsters, and have monsters lurk in caves. If a fighter dies, the miner could fight, but not very well. If all miners and fighters die, it could then be game over.
Adding other features besides caves would be nice too. Along with the fighters I mentioned, have multiple types of fighters, warriors, archers, and mages. If you dig around, make it so that some floors could have dungeons, the dungeons would have very tough blocks to break, encouraging you to send a fighting NPC through to loot the chests that would spawn in the dungeons in abundance, along with monsters.
Implementing a level system could be cool as well.
Miners gain XP from mining.
Helpers gain XP from finding stuff.
Fighers gain XP from killing monsters.
Each NPC can get to level 10 max.
Each level increases what every NPC could do.
Miners: Increased mining speed, chance re-use a pickaxe, more loot from mining blocks.
Fighters: Increased health, increased health regen, increased attack, more loot from chests.
Helpers: Increased loot from finding stuff, decreased time between finding stuff, ability to douse walls for caves, dungeons, ore, etc. (up to 3 spaces in all four directions at Level 10)
These are just my thoughts on how you could build upon this game.