I don't know if it's a bug or something but it seems that when you kill an enemy and a coin flies out and you don't get it right away that when it goes off screen it will keep bouncing on the same height in the air until you jump and see it again. It gets a little annoying when you miss a coin because of that.
Anyway, this game rocks =]
A good strategy is to save your money for the highest available gun, then save your money for the highest available shield and so on until you've got the Chaos gun because in my opinion that's the best gun of the game. Save your fire fury for the boss when you're doing a boss mission. Worked really well for me. =D
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