There's a bit of typing here, but it's worth it. This game, written entirely in machine language, is fast and flexible. You have a choice of five speeds, up to four players simultaneously, or you can compete directly against the computer. You try to control an ever-growing line without running into a boundary, another player, or yourself. For the Atari.
In COMPUTE! (August 1981) there was an action game called "Blockade," written entirely in BASIC. The idea is simple. Each player controls a line which continually grows in an enclosed box. The first player who crashes into anything (himself or herself included) loses a point. Players start with nine points, and when they reach zero they're out of the game.
The use of BASIC prevented the possibility of allowing increased speeds, multiple players, or computer play options. I wrote this version of Blockade – called "Roadblock" in machine language to add these options. If you don't know machine language you can still type it in and use it; the program contains all the DATA statements required to run the program via a USR statement.
One of the major stumbling blocks I had in writing this program was the use of graphics in machine language. Fortunately, Bill Wilkinson's "Insight: Atari" article in COMPUTE! (February 1982) came to my rescue; those familiar with his article will recognize his code.
When the main menu comes up, you are instructed to use the select, option, or start button. The option button controls the speed, from 1 to 5, where 1 is the slowest speed. The select button controls both the number of players (2, 3, or 4) and the computer play option. When the computer plays, it always plays as player number 2 and is included in the total number of players. Thus, if three players are indicated and the computer is playing, then player numbers 1 and 3 are the humans, and player number 2 is the computer.
Maneuvering around the roadblocks.