Ex-Cyber already answered, but thats how she always did it: she would make a "vertical line" in the middle of the screen with small rectangles, but without actually getting touch the other side, leaving a very very small gap where the monster cant pass. You have ~50% of the screen clear of each side, and the monster will be at one side all the time. Work from there, you can keep the space smaller and smaller , and the monster will get smaller too. When the monster can barely move because you trapped it in like a couple of pixels clear, close the rest of the screen and nab the 99.9% clear.How the heck do you 99% a level of Volfied?! That's some jedi mind tricks against the CPU right thur. I feel pretty badass when I complete level 1 over 90%, heh (and isn't 85% the minimum completion anyway?).
What's funny is that I saw her doing this so many times that it always looked easy, and I always felt stupid for not managing to do it and fucking it up every time.
Like it was said above... if it was the Genny version its quite easy to do it. I've done it myself. She used to play the MSX version, which was a lot harder, and it had all the difficulty options (It's not like the Genny version where "normal" is 5 colors and "Hard" is 6 colors. On MSX version, VERY EASY is 4 colors, Easy is 5 colors, Normal is 6, Hard is 7 and Very Hard isMy ex-g/f could counterstop it... she was playing for weeks on and off.
If that's not the hottest thing a g/f can do, i don't know what is.

I now remembered she used to play Tetris on MSX before Columns was released. She could keep on playing it Ad Infinitum. If you make more than 1000 lines the line counter just gets fucked up and stops counting... and she could keep on playing it. After Columns was released, she never played Tetris anymore.