Centipede was one of THE most-ported Atari games ever, as versions were made for the Atari 2600, 5200, the Atari home computer line, various other computers, Intellivision, Colecovision, and the Atari 7800 as well (among others I might be neglecting to mention).
This was a pretty good, close port of the arcade version in which you, as an elf (as shown on the box cover, which is a bit strange, if you ask me) with some kind of magic wand/shooter, must keep a pesky centipede out of his garden. The centipede starts from the top of the screen and makes it's way down to the bottom through a maze of mushrooms (which I'll bet a few of those were smoked somewhere during the process of developing the play mechanics of this game), which you can only shoot the centipede bit by bit. Destroying segments can break up the centipede as well, yet not slow it down in the least (must have something to do with those mushrooms, or there's something a bit wonky going on with your wand), while a spider that's worth big points (depending on how close it is when you shoot it) also taunts you, quickly darting about the playfield (which you can only move around the bottom part of the screen).
Also causing trouble in your Garden of Eden (or Garden of Smoking, as far as the mushrooms go) are a flea that will appear and re-seed the screen of mushrooms (if fewer than five mushrooms are in your playing area at any time, expect a visit from him), and the most dreaded of them all, the high-scoring scorpion, which poisons mushrooms, which, if the centipede comes into contact with one, will send it plunging all the way down to the bottom of the screen, rather than just forcing the menacing critter from (garden) hell to drop down a level once it comes into contact with a normal one.
I only paid two or three bucks for this game at a liquidation sale in the early 90s, only playing it once, then shelving it for years until I got back into my 7800 in 2002 or 2003 (since I had gotten a Genesis and was playing around with that for nearly 10 years), since the game's a lot easier than it's arcade counterpart. However, if you just raise the starting difficulty level up a notch, it's more fun, as I found myself barely being able to hit the 30,000 mark then, rather than 200,000 on the default easy level. (Good thing I changed my mind about getting rid of the game, too!)
Plus, there's a simultaneous two player onscreen variation as well, which is very fun. This wasn't on the arcade original, either, so having this in the game really ROCKS!
Also rocking is if you have a trackball controller, which makes it even more like the arcade version, rather than using the damn joystick for this game, which, even though the controls respond fine, it isn't the same.
About the only thing wrong with this version is the stupid outline border around the screen, which is annoying to look at. Why the hell is that in there? Dunno, but it bugs me (pardon the pun). Other than that, though, this version's a blast. 9/10