are issued (such as ordering the construction of a building), with the AI handling the delegation of orders to specific settlers. However, the player can control specialist settlers, of which there are four types; pioneers (extend the player's territory by digging at the border), thieves (scout enemy territory and steal resources), geologists (test mountainous ground for raw materials), and gardeners (reclaim terrain corrupted by the Dark Tribe). When playing a multiplayer game, the player also has access to a fifth specialist unit; the Saboteur, who can attack and destroy all enemy buildings, not just military installations. As in The Settlers III, players do not have to construct a road network. Instead, settlers can walk freely around the player's territory, with the AI handling pathfinding. Like all previous games in the series, The Settlers IV has an adjustable goods priority system, which determines the order in which items are transported. Players can also build marketplaces, which allow for the establishment of trade routes between areas on the same geographical region, and shipyards, which allow for the manufacture of warships, ferries (can transport specialist settlers, soldiers and war machines) and trade ships (can transport items from a landing dock to a different geographical region). Races and economy In the original game, the player controlled three races; Romans, Vikings and Mayans. The Trojans and the Elixir of Power added the Trojans as a fourth race. As in Settlers III, each race has a slightly different economic model. For example, the Romans' and Trojans' construction industries require roughly equal amounts of wood and stone, the Vikings' more wood than stone, and the Mayans' more stone than wood. Each race also has specific skills; for example, only the Romans can produce manna using only two buildings; only the Vikings can build war machines and warships which use manna rather than physical ammunition; and only the Mayans can utilise desert terrain (to grow agave plants necessary for the production of tequila). The economy is under the player's control throughout the game. For example, the player can control the distribution of goods by selecting which percentage of a given resource is transported to a given building. In a similar manner, the player can select what tools are made when. Tool production is important insofar as all buildings require raw materials and a worker with the right tool. For example, if the player has built a mine, and