Very good little title you got here, I'm looking forward to it.
To reiterate what others have said, I agree that movement is a bit limited, as well a bit stiff. Up being the only consistently speedy direction you can go. I also had the issue of finding movement very slick, with it being very easy to slip off single-tile pillars, and the icy momentum the character has even on flat ground.
Something I noticed, is that using un-upgraded items was vastly more efficient than using the upgraded versions. Not only in fuel usage, but also in controllability, especially with the weapon, where the rifle wastes far more fuel in a single area where explosions will overlap. As such, that is what I reverted to after purchasing the upgrades, which is why I did not have the issues others brought up regarding not being able to break even with profits vs fuel usage.
Something I would personally suggest, is some way to tell depth other than ores. Due to the ability to see the skybox behind the character at all times, it feels you are perpetually near the surface, making vertical navigation somewhat surreal.
I must state however, as your Steam trailer shows a very different game compared to this demo, these are likely a moot points.
Best of luck on the final product.