Upgrading as soon as possible is often NOT the best strategy. Often times it is wise to keep some cash on hand so that you can react if necessary. While some of the short 10 wave levels took a few tries, I was able to pass all of the marathons on the first try, and I didn't once use an advanced unit.
Sancdar, that's the strategy! You have to make sure you have enough firepower to pass the current level, while still being diversified enough to pass future unknown levels.
Okay. This is a FAR better version than Defender. Good job taking user thoughts into consideration, if that's indeed what you did. Oh, and just so people know, you have to click "Submit Score" for it to register on Kong. I'm sure I won't get to keep the all-time score for long when people find out. :-P
I'd be interested in a utility that's a telescope. It could have a max and min range, say 8-12k and allow you to lock on to a target, letting you know what's ahead if you don't have long range weapons.
Not sure quite how this game is ranked so highly... I thought the career was very easy, as I was able to pass through with very few repetitions and minimal tactics beyond ganging up. The challenges were just downright annoying... the concept is workable, I was just surprised to be so disappointed.