I great way to spend a lazy afternoon. It was a little slow at the start, (until I figured out how to kill the grey and red moving rocks without getting killed) but it never felt grindy. If fact it was nicely balanced, every time I started to get board I would find a new weapon or open a new area.
I wasted a lot of explosives by accidentally hitting the X- key instead of the Y-key; Consider changing the X-key to the E-key.
Also, consider moving the ore bins inside the store when I was inside shopping I kept forgetting how much of each ore I had to spend.
Do we earn something for watching ads? I assumed it would heal my health points, but I don't think it did.
It was the perfect length and difficulty for the type of game I was looking for today. But if this was just a demo, I'm looking forward to the full length game.