Chopper Command, of course, was Activision's ripoff of Defender. Atari's port of the arcade classic for the 2600 has been criticized harshly over the years (I happen to enjoy the game, but that's another story). Activision, however, one-upped Atari by producing a game which utilized the Defender concept and was far superior to the licensed product for the 2600.
Chopper Command puts the player in control of a helicopter and given the mission of protecting convoy trucks from enemy attack. The playfield is a scrolling screen filled with enemy helicopters and planes which busily throw bombs at the convoy. A very nice feature of the game is a radar screen which allows the player to track trucks in the convoy as well as enemies. The game would be difficult as all get out without the radar as the game takes place over a large area, and the player can only occupy a small section of the playfield at a time.
Sound easy? It's not. Sure, the first few levels of the game are easy enough, but the enemies just get faster and more aggressive with each level (a level is cleared when all the enemy planes and helicopters are destroyed). At higher levels, the enemy aircraft is downright difficult to avoid, partially because of the speed of the game and partially because the player has a huge helicopter which is an easy target.
To make matters worse, inertia is figured into the game. If the player decides to turn the helicopter around and fly off in a different direction, it takes a bit of time for the vehicle to respond to the rapid change. Couple the inertia feature with rather stiff controls, and dragging the helicopter out of harm's way gets downright difficult at higher levels.
The graphics are classic Activision - simple, well-defined and flicker-free. Well, the radar screen flickers a bit, but that actually "adds" to the game a bit (radar screens are supposed to be a bit fuzzy, aren't they?) The sounds are also about what you'd expect in that the user is given enough audio clues to know what's going on (gunfire, explosions and etc.), but there's nothing really earth shattering in terms of audio.
The only real complaint I have about the game is that it tends to get repetitive after a time. However, that's to be expected of most Atari 2600 games, right? Also, the insane difficulty on higher levels can make the game a bit frustrating.
Still, if you're not happy with the 2600 version of Defender and you don't want to seek out the superior, but rarer, Stargate, the very common Chopper Command might very be one to add to your collection. Heck, if you just want a good shooter for the 2600 that will test your reflexes, this game won't disappoint you at all.