Eastern Front (video Game) - AI

AI

The computer AI calculated its moves during the period between vertical blank interrupts (VBI). The rest of the game, what the user saw, was run during the VBI period of a few hundred cycles. According to Crawford in Chris Crawford on Game Design, the system started with a basic "plan" and then applied any available cycles to trying variations on that plan, selecting higher-valued outcomes. A few thousand cycles were available between each VBI, so given a typical order-entry phase of a minute, the computer had millions of cycles to spend on refining its plan.

The AI was based on three basic measures of the game state: the strategic situation which attempted to take and hold cities, the tactical situation which attempted to block player movements, and the overall arrangement of the front line. The AI would first attempt to build a continuous front line in an attempt to prevent encirclements, it would then send additional units on intercept courses to block player movements, and finally any remaining units were sent to undefended cities.

Although the AI was not particularly strong, it made up for this with numbers. Against a player "playing fair" the computer could put up a credible defence. Direct fights were hopeless, as newly arriving units would eventually overwhelm the German forces. Crawford spent considerable time "tuning" the arrival of new units to balance the gameplay. In typical games, the player would attempt to break eastward, and encircle the ever-growing block of Russian units. The Russians were short of the highly mobile armored units, at least early in the game, so it was possible to outmaneuver them and cut off their supplies, drawn from the far right edge of the screen.

Unfortunately, there were ways to "game" the AI. One was to break the German forces into two blocks, and then advance them on alternate turns. The tactical part of the AI would attempt to intercept these movements, sending its mobile forces first one way, then the other, never actually making contact. Another strategy was to keep flanking forces behind a spearhead, which the AI would attempt to block. This would result in the computer forces clumping up in front of the Germans, allowing the wings to move in once motion was difficult.

One "bug" in the game engine was later exploited by players. Since the AI calculated its moves while the user entered their orders, reducing the amount of time the user took to plan their own moves reduced the quality of the computer response. This could be reduced to zero by pressing the Start key repeatedly, at which point neither the player or the computer would do anything. This way combat during the winter could be avoided entirely, allowing the player to break out the next spring with full-strength units.