There are 3 screens that repeat.
1 Main level, where you shoot advancing enemies above and below you.
2 Bonus stage
3 Boss stage, with bouncing shots.
You have plenty of men to do this with, so try to keep as many as possible
throughout each level. (You can lose a few and still make it though)
For the first.
Master shooting diagonally to the upper left. I just move back and forth and shoot
up and diagonally. Ignore the enemies below you. I don't think you even get points
for hitting them. Points run up as long as you last.
WATCH OUT FOR HORIZONTAL BULLETS on the latter waves, you need to shoot
them also, or you will lose a man.
Bonus stage gives you a few points. I just move to the upper left, and shoot diagonally
to the right most of the time.
For the Boss stage: AVOID HITTING OR TOUCHING THE BOSS or you will lose a life
1 bullet - just chase the bullet around and shoot the boss
2 bullets - just chase one of them, while avoiding the others, (These speed up)
3 bullets - they just slow down at this point, so shouldn't be too hard to avoid
If you get to the 3 bullets levels, you should have enough to get the 20k
Here's how i got it, (i lost several men, and played poorly, but still managed):