Single player also has the option of "Ironman" mode, which locks several settings such as difficulty, and removes the control of saving the game from the player. Players can choose to play single player mode versus the AI, or multiplayer over a LAN or the Internet against a mix of human and AI opponents. Some of these random events are driven by an individual country's history, while some can apply to any country and serve generally to enhance the "flavor" of the game. These events can be either helpful or harmful. Gameplay is influenced by random events that arise every so often for the player. Military technology unlocks advancements such as new types of land units, improved unit morale, combat tactics, and new buildings.Diplomatic technology unlocks advancements such as naval units, improvements in trade, new buildings, and improved colonial expansion.Administrative technology unlocks advancements such as increased productivity, new forms of government, new buildings, and the national idea system.They provide benefits to the nation as detailed below:
Technological advancements are invested in over time, and require the expense of monarch points. For example, the Catholic faith makes use of the Papacy, which can allow a nation to have control over the Pope or to use their influence for other rewards. Players can employ missionaries to convert their provinces or can engage in policies of universal religious freedom. Many major religions, such as Catholic, Orthodox, Protestant, Sunni, and Shia are present in the game and can provide distinct bonuses to their practitioners. Trade is also an important part of the game, where the world is divided into many trade nodes and trade flows through each of the nodes and can be collected by merchants. Combat can be waged on both land and sea, during which the game attempts to simulate real world factors such as morale, discipline, varying unit types with associated strengths and weaknesses, competency of leaders, terrain and supply lines. Espionage can also be employed against enemy states in order to claim their territory, or incite rebellion in their provinces, along with other dubious ends.
Diplomacy is a large aspect of the game, as creating alliances, (or vassal states and tributaries), improving opinions, and preventing defensive coalitions are vital to a player's survival. The game is a sandbox environment, and while there is no strict rule on winning the game, the game of the player is over when the player's nation is removed, or annexed, from the map. These nations range alphabetically from Aachen to Zuni. Players can choose to conquer the world by military might, become a colonial superpower, establish trade dominance, etc. The player does so through their choices as sovereign of their nation, and through the spending of resources available to them: Prestige, Stability, Gold (Ducats), Manpower, Legitimacy for Monarchies, Republican Tradition for Republics, Devotion for Theocracies, Horde Unity for Hordes and Monarch Power (Administrative, Diplomatic, Military). The gameplay requires the player to lead a nation by finding a balance of military, diplomacy and economy. Each of these provinces contribute to their country either positively or negatively, as provinces can both provide resources to a nation and serve as a point of unrest and rebellion. The game itself is an interactive map of Earth divided into the provinces that compose nations.
The game has been formed to begin historically, with events occurring when they did in history.