Things I liked about the game: The art, the music, the character designs, the voice work. Those appear to have more work put into them than the rest.
For the rest, it's a nice idea but there's trouble in execution as others have mentioned. It also has bugs. The 'R' key refuses to reload the level sometimes, which is particularly frustrating. And the music from the boss fights doesn't always end when the level does, leaving you with two songs playing.
There's very few platform elements to the game, making the running-around mode almost redundant. I'd have put some puzzle elements into the platform part -- you could do things like flip switches to open paths.
The first two boss battles (Haven't made it to the third yet) appear rather phoned-in. The boss robot looks unimpressive; it's a head and three squares. It doesn't even have any sound effects when its weapons fire, though the villain rants at you. You can't fight back even though you're a mole with drillhands driving a digging machine, you can only dodge and run.
It's also plagued by fridge logic. WHY does he have drill hands that can't drill anything!? Why can't he go through the level in the drilling machine that brought him there? (I'd have made it a fixed drilling machine, with a shaft to the surface, easy explanation.) Who left all the digging machine portals and millions of landmines? Why can't he just fire the turbos and outrun the boss battles? ...Why DON'T the turbos fire when he DOES outrun the boss battles?
Nonetheless, a simple and fun game, and I look forward to seeing what happens at the end if I can make it that far.