It's definitely a great game. Very addictive to progress and upgrade. I maxed out everything and got past the max depth on the gauge. Graphics are nice, but could be better.
Some suggestions:
1) tweak code on magnet so if treasure comes within the magnet's pull you collect it no matter how fast you're moving
2) make the pointer a distinct, easily visible object. it can be hard to see where you are pointing when there is a lot of objects on the screen
3) ending/storyline
4) longer and deeper game with more upgrades that progress more slowly?
5) make everything smaller and/or the game screen bigger
6) more graphic background objects/animation
7) secrets (if there are none already)