Here are a few tips to help you out in your snake-slaughtering:

Give the snakes some room. Learn how they move. Remember that some snakes make a little spinning move when they change directions, you don't want to be close when they do that or they will get you. Don't let them force you down the screen.. move up and around sometimes to get above them. They will follow you up and the more room you have beneath them the better your chances are. This leads to the first useful move in the game.

The Push:

When you have snakes converging on you from the side you can push up just a little to get above them. They will turn and move diagonaly, which should make them shoot up above you where you can slaughter them.

The Slide:

Remember that snakes will (mostly) not move outside the visible playing area. This means that they're likely to turn on the edge of the visible screen, allowing you to quickly slide over and up the edge of the screen behind them. A nice way out of a tight spot.

It's also important to keep an eye on the activity in the background. You can tell (approximately) how many snakes are left in the level by looking into the grid in the center of the screen. Small one-pixel snakes writhe around in the background there, and when they're all gone then you're quite close to the end of the level. It's also essential to your survival that you watch for the green swoops of snakes and other foes rezzing into the level. If you see a bunch of pixels converge on the side of the screen.. FOR GOAT'S SAKE KEEP AWAY FROM THAT EDGE until the snake is out on the screen. You don't want the snake rushing in from the side (where you have little firepower protection) and smashing you.

And don't forget your emergency friend the sheepie-zapper. Click your right mouse button when you're in a tight spot and watch all heck become unleashed. It's always a risk because it clutters the screen with exploding foes, making navigation difficult, but it's worht it for the evil thrill of unleashing all that firepower. (Warning: at this time you risk a crash when you utilize the sheepie-zapper. Zap at your own risk.)