Here's a little tip:

It's always a pain to fight and fight to level up your weapons, correct?
It takes FOREVER
Here's a little trick on leveling them up with no threat to your lives or health.

Here we go:
After you beat the intro stage, you can go back to the underground laboratory.  Go there, and find one of the little lumps of thread that shoot out spiders. These will not only spit out seven at a time, registering seven enemy defeats to four weapons, but they release seven MORE just two or three seconds later.  I have found this very useful.
However:
Do NOT complete the "retrieve data" mission until you are COMPLETELY satisfied with your weapons level, as the security system that will try to destroy you at the end of the level will seal up everything other than a small area at the top of the tunnel.  In other words, once you complete this mission, this trick will no longer work.

If it's going too slow and you think that it isn't working fast enough, use....the speed button!
Have fun with your upgraded weapons!

-Hidden Phantom

You need another post, that one tip is old