In my original build the controls were fairly unintuitive and hard to get used to. I have since updated the build to use mouse controls for gun aiming and firing (firing may still be triggered using the keyboard as well).
The new control scheme is:
A/Left – move counter-clockwise
D/Right – move clockwise
Mouse Move – gun aiming
Left Click – fire gun
Right Click – drop charge
C – drill
The new builds may be downloaded from the following locations: