My first game was 81.
I've found you can sit in the corner of the screen and never move except at "key" points. I forget the first key point off hand, but the second one is at 44 points. You need to move for a second then you can safely go back in the corner and sit for awhile until #3.
EDIT: Okay, so here's the strategy.
1 - Sit in top right corner until 17 points. Avoid enemy and go back to corner.
2 - At point 44, avoid enemy, then sit in corner again.
3 - At point 72, avoid enemy, then sit in corner again.
4 - At point 75, avoid enemy, then sit in corner again.
After that you can figure it out.
Note, you said you stick along the top wall.. a better place to stick is on the right side wall. Two reasons IMO.. 1 - your enemies always come out from the left, 2 - the right side wall is shorter than the top wall.. less space to worry about enemies hitting.
Here's the end result of that game:
Edited by yuppicide, Sun Jul 5, 2009 12:36 PM.