The game starts with the player engaging in a test to become part of the "Raven's Nest". It simply involves destroying two Muscle Tracers (MTs), before being destroyed oneself. Upon passing this test, the player receives mission requests from corporations and other groups. Missions generally pay higher as difficulty increases, and payments can range from money to prototype AC parts. Depending on which missions are chosen, the story progresses differently. The player can also read mail from various senders, and observe their rankings, which are based on mission success rates. The player is responsible for purchasing their weapons and AC parts, and must use the money they earn from missions to that end. There is no way to replenish ammunition or armor during missions, so the cost of resupplying ammunition and repairing AC units is automatically deducted from the player's payment at the end of each mission. If a mission is failed, or if the payment is a prototype AC part, the cost of repairs and ammunition is deducted from the total amount of money the player has accumulated. One notable aspect regarding the parts, particularly weapons, in the original Armored Core and its two PS1 expansions is that they are by far the most powerful in the series. For example, the original KARASAWA fired faster than most AST Rifles and Pulse Rifles in later games. The FINGER had 3000 ammo, and the Large Missile came in two styles, one that flew like a regular missile (discontinued after Master of Arena), and the traditional slow (though roughly twice as fast as later versions such as those in Last Raven) version. The slow version had ten missiles as opposed to the current four, and was the longest range missile of the first generation.