Very good!
I'd advise that you play the full version for maximum enjoyment. You can save, for one thing, which is nice.
I made it down to about 5000 and then I died. :sigh:
My tips for people just discovering this game: upgrade your gas tank first. First thing you should do. Once you buy the second upgrade, you have a bit more freedom of movement. I tend to drill a long, straight down shaft right next to the fuel station. I go to the side from time to time to get the good stuff (silver and gold early on) but maintain the direct shaft. When you have about a third of your tank remaining, go back up. Sell off everything you have and pick some upgrades if you can afford them. Upgrade your cargo hold to at least the second one, I'd recommend the third, as soon as possible...the bigger the bay, the more you can haul in at the end of each trip.
Keep a mental note of how deep your primary shaft goes, so you can slow down and not take damage.
After a while, when platinum starts showing up and money becomes easier to get, buy some fuel reserves and a matter transporter and then you're free to have longer and deeper trips, with more exploring. And before you venture past 4500 or more, UPGRADE YOUR HULL. TRUST ME. You do not want to die from a natural gas pocket all of a sudden like I did.
I loved this game. Very time consuming, very addictive. Thumbs up to XGen.