What a Grind. Candy Drill. It is not skill, it is just plunging down 500 times, so that I have enough material and plasma to upgrade my durability and energy enough to get to 500 meters. Yuck.
I've played a lot. High score is 21,340. My thoughts: (1) Anchors should be slightly more plentiful and/or regular after the defeat of the first set of final bosses; and (2) The second boss' eyeballs take too many hits - even when I go into that fight with a big gun, there are still nearly all of the eyeballs remaining when the ship goes down.
1) Skip the money bags, unless the path is clear, or blocked by a weak monster. Usually, the cost of health lost is greater than the money gained.
2) fight into all of the chests - even if the bad guy is a tough one. Strong equip-ables = big money.
3) Don't spend money on equip-ables unless you are starting a level with the basic weapon or armor. Chests are everywhere. Save $ for health.
4) Save your best equip-able artifacts, and sell the rest for health.
5) Amulets: keep +Fire def., +Earth def., and +instant kill. Sell the rest for health.