cancelled by pressing the . After entering orders, the combat phase begins with . Units attempt to follow their orders to the greatest extent possible, delayed by terrain, blocking friendly units, or combat with enemy units. The screen shows combat by flashing the "attacked" unit, which might be forced to retreat, or be destroyed outright. When all possible movement and combat is exhausted, the game returns to the order-entry phase. Each turn represents one week in-game time, and the game ends on 29 March 1942, after 41 turns. The game engine includes a number of features that increases the depth of the simulation compared to contemporary wargames, such as zones of control, which allows front lines to be constructed without requiring contiguous lines of units. This includes muster and combat strengths, which simulates losses due to combat, and reinforcements that slowly returns a unit to muster strength over time. Supply lines are also simulated, and surrounding the enemy to cut off their supplies is an important strategy for the human player, who faces an overwhelming enemy numerical superiority. The game simulates the changing of the seasons: 14 turns of summer that begin in June 1941, four turns of autumn, and 22 turns of winter. When autumn begins on 5 October 1941 and the green land changes to purple-brown mud, the player is likely losing if they have not captured most objectives, destroyed most early Russian forces, and established a defensive position. Victory points are scored by moving German forces east, capturing Moscow, Leningrad, Stalingrad, and Sevastopol, and destroying and pushing Russian forces east. The highest possible score is 255, and the documentation suggests that any score above 100 is good. Computer Gaming World estimated that the actual German army in 1941 scored 110 to 120. A high score by early autumn is not difficult but keeping it high during winter is almost impossible, as mud and snow appears, rivers and land gradually freeze during winter, and Russians counterattack; until the spring thaw the German side is forced into a purely defensive role. If the player survives until spring the season offers a renewed offensive capability, but only for a short period before the game ends. Artificial intelligence In an example of pondering, the computer AI calculates its moves during the period between vertical blank interrupts (VBI). The rest of the game, what the user sees, is run during the VBI