Interesting concept! This seems like it wants to be a sort of simplified "1D" digging game like the 1D pacman game (paku paku, made by Kenta Cho). In this case though, I think it would feel better if we could dig left and right as well as down. Otherwise there's really no reason to move to another column, since resources will be random anyway, so digging in one column is as good as any other.
Being able to extend the time period through upgrades would be more meaningful if we could dig in other directions too, since we'd have more time to dig around the deeper we went.
Might be interesting to consider "echoes" from the previous time loop, like the path that was dug out is still there (but goes away by the next loop), or maybe the digging/timing is overlayed on the current loop.
Seems like the start of something, but not quite a game yet... Congrats on submitting it though!