that looks pretty cool! i like these kind of very simple games; they are so honest about the one thing the game revolves around. they avoid much of the non-gratifying sloth by staying close to their core.
the mining part reminded me of clonk
, although that is an entirely different affair. it is more complex, but i always got a similar feeling of accomplishment when harvesting resources & building something from them. it also worked awesome in cooperative multiplayer.
about wasted time: i'm also concerned about wasting time with these kind of games, which is funny, because i don't have that strong a feeling of time-wasting with other, more complex games. arguably, i'm still wasting the same amount of time regardless which one of these i play, right? what do you think of this analogy: i feel less guilty about reading a book that has an intriguing story, an accomplished author, or is scientifically relevant, than reading a book with white pages just because i like the way the book feels in my hands? it's basically the guilty joy of pushing buttons ;)