I've read some reviews comparing this game to Pole Position, and that's not exactly fair. Pole Position for the 2600, while enjoyable in its own right, is an arcade racer, while 1983's Enduro is more of a simulator which almost seems too sophisticated for the old Stella console.
Enduro, as the title implies, drops the player in a cross-country, endurance race which is divided into days. On the first day, the player hits the road at sunrise and is given the chore of passing 200 cars before the day is done. If the player manages that, he is to pass 300 cars, and the difficulty ramps up on each subsequent day. While passing a certain number of cars might not seem to challenging, the days pass quickly and the opponents become faster and more reluctant to be passed as the game progresses. If the player makes the mistake of hitting another car, you get the static-filled "explosion" noise and wind up on the side of the road as cars pass.
The structure of the game itself provides a challenge as the player has to deal with changing weather conditions and, of course, darkness. The true brilliance behind the game can be found here in that the changing weather and time-of-day have a noticeable impact on either visibility, the handling of the car or both. The player will have to put up with snow, rain, fog and darkness throughout the game. Snow, for example, makes the car quite difficult to control in that the handling is fairly sluggish, but the vehicle can get away from you in a hurry. When it's night, the opposing vehicles are reduced to mere points of light (taillights, see), which means the player has to reduce his speed and negotiate carefully. Weather conditions and darkness require the player to revise his strategy so as to avoid the time-wasting accidents. The darkness is particularly troublesome if the player needs to pass a lot of cars before the sun rises and the next day begins.
By the way, times-of-day and changing weather conditions were utilized very well in another outstanding Activision game for the 2600 -- Robot Tank.
Graphically, this game is pretty simple - the road is represented as two lines which shoot at the driver from the horizon while twisting and curving as a natural highway might. Speaking of the horizon, keeping an eye on it is key to figuring out when night is approaching, when the sunrise is close at hand and etc. As usual with Activision games, rainbow sunsets and the like are utilized well in the horizon. The player's car is an ill-defined, white blob which isn't pretty, but serves its purpose. The opposing vehicles are of various colors and are scaled well as they make their way from the horizon to the player's car.
The controls are excellent. The joystick is used to steer, brake and accelerate, and the vehicle truly become sluggish under some of the aforementioned weather conditions.
The sound is best described as utilitarian. Rudimentary audio cues are utilized to let the player know when he's passed a car and when he's completed his daily goals and a new day of racing begins. Explosions, as I mentioned, sound like static.
The only drawback to this excellent game is the fact that it does take a lot of time to play and there's no way to save (naturally) or skip past the lower levels. Still, this fairly-common cartridge is a joy and should be appreciated by anyone wanting a good racing game for the 2600.