I can only agree with the previous poster about the problems of this game. As the number of fish grows, the game becomes intolerably laggy. The boundaries of the area are invisible, and since there are fish you should be able to eat outside those boundaries, it gets confusing.
Also, the shark is simply unfair. It appears at random and eats you. You have no hope of dodging it, if you're in its path when it appears, you're dead. That is not good game design: you need to be able to avoid dangers.
After playing this a few times, looking for new strategies, I figured out the Rav Gas rounds are excellent. Using those, you can kill everything in waves 23 and 25, which are otherwise nigh unbeatable without superweapons. But...
You get a lower score when using those rounds. Why? Because high score is based on ravagers killed and money spent, and the Rav Gas rounds finish off those black ghost things too fast. When they die, they don't summon any more basic ravagers, and you don't score for killing them.
Thus, you get a higher score by using weaker ammunition and leaving the ghosts alive to summon more ravagers. When you're about to be overrun, then use the Satellite Rain, and get a high score for killing lots of weak ravagers in one go. It is stupid, but the game rewards you for doing it that way.
SAW, M60 and M2 are in my opinion the only things worth getting, as soon as you can afford them. Of the mods you need HiCal, Armour Piercing and High Explosive rounds. Armour Piercing is of course for those ravagers who raise their arm to guard themselves, as well as the giants jumping up and down. High Explosive rounds work wonders against anything small, particularly the running ravagers and those enemies jumping left and right, killing them quickly so you can concentrate on the main mob. HiCal for everything else. Also, you pretty much need two Satellite Rains for waves 23 and 25, and of course you need to repair. One useful tip I discovered was that you can leave one slow enemy alive at the end of a level, and while that slow enemy walks toward you, you have plenty of time to use light repairs and wait for it to recharge, enabling you to use repairs without waiting on the next level, which can be a lifesaver.
It's a pity that some of the weapons just aren't worth buying. In fact, some of them are so bad that you're likely to lose if you waste your money on them, instead of things you actually need.
One bug/design flaw I've noticed is that frequently when you try to aim at something on the edge of the field of fire, the cursor actually moves outside the game window. Then, when you click and try to fire, the game window loses focus and no shots are fired. This is very annoying, as it can cost you a couple seconds each time when you need to be quick at aiming and shooting. To prevent this, perhaps there should be a buffer along the edges of the game window.
Mission 14 needs some kind of tweaking, it is now too difficult relative to the others. Even after I figured out how to aim the bombs, I kept missing radars every so often. Perhaps a distance counter to the next radar would help?
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