i was expecting an actual digger & upgrade game, not just a "let's outrun the lava as fast as we bloody well can." on the other hand, it's an interesting concept. i'd say that it needs some refinement: perhaps an money and upgrade system that makes it easier to start progressing deeper, and perhaps a little less random in general as it's easy to get trapped pretty much anywhere from the get-go.
i have no idea what this lag issue is that people are talking about. my computer is old enough that it's usually the first to start suffering from lag and freeze issues, but it's working just fine for me, so go figure.
on the other hand, i gotta say that the background music, while catchy at first, is not something one can listen to for very long. on the contrary, whether it's grating overload of synthetic instruments--sawtooth, polysynth, atmosphere, etc--or simply the sheer cheesiness of it all, the option of the mute button is all too necessary. it's not a variety issue. it's not really a matter of good or bad writing either. it's just a matter of tact: it just doesn't work all that well together overall.
anyway, not a bad presentation, but there's definitely room for improvement.