An easy way to get a lot of money is to only upgrade your health and keep playing Level 1 over and over. You get money just for having health remaining.
To get the "Can't get enough" achievement super easy, play this level 5 times:
999999999999999999999999999999999999999999999Be999999999999999999999999999991
3/5 currently, easily 4/5 with changes already mentioned:
* pause button
* LMB should freeze gun, not ship (stopping motion is a death sentence with all the bullets flying at you)
* enemies shouldn't spawn near you
* when you die, you should keep the crystals you've collected
* money magnet
Yeah! Second highest All-Time score, not counting the cheater.
=D
This game is great. I've played through seven times as different people, done most of the paths you can do, and I'm only just starting to get bored of it. One of the few 5/5.
For those confused on level 12, besides 5/5 powered and 12/12 nozzles, you have to have all nozzles of the Power Cells putting out power (even though it doesn't list this at the bottom).
Gear games stink. It's just trying to find how to get it all to fit up. Not hard in a good challenging way, hard in a frustrating "how in the world do I connect these??" way.
Decent as far as gear games go.
2/5