Core Modding Principles

**Event Structure**

Rule 1: No event is to have only 1 option unless a prior event triggered this event and that prior event gave an option to avoid the subsequent one option only event.
Rule 2: As a general rule, all historical or ahistorical events should be fire_only_once = yes
Rule 3: Historical and ahistorical events should check for government = X, is_vassal = no/vassal_of = X and war = yes/no
Rule 4: As a general principle, money should only be removed through event ot decision if there is a check to ensure that the country has sufficient money. This is avoid an unintentional bankruptcy by the AI.
Rule 5: All options should have at least some AI chance of picking it. For historical events, the AI chance for the historical option cannot be below factor = 0.8

**Province or Country Annexations or Vassalisation or Granting of Independence by Event/Decision**

Rule 1: No province can be ceded from country A to another country B through event unless: (1) A is not a vassal and B is not a vassal; (2) A actually owns the province; and (3) A was given a choice not to cede the province to B in the event.
Rule 2: No province can be the subject of any event or decision's effect unless: THIS owns the province.
Rule 3: No country can be made a puppet of another country or annexed by event unless: (1) both countries are independent at the time; and (2) the country to be puppetted or annexed has a choice not to be puppetted or annexed.
Rule 4: No ceding of ownership of the capital of any country by event if that country is to remain on the map post annexation of the capital province.
Rule 5: No country can be released via event unless: (1) there is a check of is_possible_vassal = TAG by THIS first; and (2) THIS is independent.
Rule 6: No event can trigger a war between 2 countries unless: (1) both countries are independent; and (2) the aggressor had a choice to avoid the war.

**Alteration of Government Type or Ruling Party by Event/Decision**

Rule 1: No government type can be changed via event unless: (1) THIS is not a vassal; and (2) THIS had a choice of avoiding the change in government type in the event. Overlord can change gov types unilaterally.
Rule 2: An event changing ruling parties must have a check for the appropriate government type as not all gov types allow all ideologies.
Rule 3: Change in ruling party in democratic nations cannot be done when an election is ongoing.

**Changing Relations or Influence by Event/Decision**

Rule 1: No relation with any country can be modified unless: (1) there is a check for the country existing; and (2) the country is independent (use: random_country = { limit = { tag = TAG government = X is_vassal = no } relation = { who = THIS value = X } } OR random_country = { limit = { tag = TAG government = X is_greater_power = yes } diplomatic_relation = { who = THIS value = X } } )
Rule 2: No war is to be trigged by decision.

**Tag Creation, Cores and Provinces**

Rule 1: Country tags are to be created based on geographical locations rather than government types. So, for example, there should not be a GDR tag for only communist Germany but a tag for East Germany is fine.
Rule 2: No special tags for civil wars are allowed to have cores on any part of the map.
Rule 3: All special tags must have a catch all clean up event to remove them.
Rule 4: United countries should use a separate tag as far as possible. Example: LBY tag with separate FEZ, CYR and TRI tags.
Rule 5: No provinces are to be created solely for one purpose. So example: no provinces are to be made in German just for the US to have bases in Germany.
Rule 6: The default name for a TAG should be based on geographical designation and not government and not identical or similar to any other country. Example: UGR's default name cannot be called 'Communist Greece' because GRE can also be communist and it can lead to monarchy UGR being called "Communist Greece".
Rule 7: Party names for any country cannot exceed 31 characters (including spaces).
Rule 8: One Province States should be avoided at all cost unless absolutely necessary.

**Localisation**
Rule 1: Localisation should not use special characters as the game engine is unable to read them properly.
Rule 2: Localisation should not be so long that it spills out of the UI.