Events/Mechanics

Usual Mechanics
In every event, there are several gameplay mechanics that are implemented, some of which are exclusive to Events. These mechanics may change the gameplay drastically. New mechanics are usually introduced to the game with each event.

Combined Fleet
The Combined Fleet system was first introduced for the Battle of Midway during the Summer Event of 2014, and has been present as an event-exclusive mechanic since. In a Combined Fleet, you'll have to organize and sortie the first two fleets together, allowing for up to 12 ships (instead of the usual 6) to be sortied out at once. Combined fleets can only be sortied to the maps that requires it. See the dedicated page for more info about combined fleets. back to Table of Contents

Ship Locking
Introduced since the Summer 2014 Event, as its name suggests, this mechanism locks the ships that you had sortied out to specific event maps and will be unable to participate in other ship-locked maps. A ship girl will receive her lock as soon as she sorties to a ship-locking event map. After that, it's impossible to remove the lock till the end of the event. Remodeling or marriage will NOT remove the shiplock. However, this locking system is only applied to that ship's specific ID, so any other ship with same name will not gain the lock. Support expeditions will not receive locks.

Here's an example from the Summer 2015 Event:
 * Sending Shimakaze to E-1 and/or E-2 would lock her to E-1 and E-2 and thus were unable to participate in the subsequent maps until the final map.
 * Sending Nagato to E-3 would lock her to E-3 and E-6 and thus were unable to be sent to Map E-2, E-4 and E-5.
 * Sending Kongou to E-4 would lock her to E-4 and cannot be sortied out to subsequent maps until the final map.
 * Sending Yamato to E-6 would lock her to E-6, but she can participate to E-3 which has similar tag.
 * Sending Kitakami to E-5 would lock her to E-5 only, effectively locking her out from the rest of the event maps.
 * Sending Akitsumaru to E-7 won't lock her to any map, and is free to participate in any of the earlier event maps until she is actually sortied to any of them, from which their respective ship locking are applied.
 * All the aforementioned ships were able to participate in E-7 on C-rank (Easy). However, Kitakami was unable to participate at higher difficulties as E-7 doesn't allow participants from E-5.

This mechanic varies for each and every event, so make sure you check the specific Event pages themselves for more info on which maps are locked. This is also a reason why you should keep multiple ships per ship-type prepared. If you lack a surplus, you may not be able to fulfill branching routes on further maps or may be forced to use a very difficult composition.

Support expeditions do not check for ship lock, with the exception of Summer 2014 Event (AL/MI). back to Table of Contents

Difficulty Selection
Starting from the Winter 2015 Event, players can choose from the difficulty they want to play on each event map among three available difficulties: easy (丙), medium (乙), and hard (甲).

Differences
Different difficulties yield different rewards with harder ones either giving more items, or better versions of the same base item type. However, ship rewards are always given regardless of difficulty. Drops also differ with some ships available only on medium to hard maps, and drop rates are increased for some ships on higher difficulties. Enemy compositions also differ, where bosses and their escorts are usually weaker on easier difficulties. Whether it is more efficient to farm with a lower drop rate on an easier difficulty or with a higher drop rate on a harder difficulty depends on the differences in drop rates and the potential of the Admiral's fleet.

Ship locks, if applicable, will be placed regardless of difficulty, but will only be enforced on Medium and Hard difficulties.

Clearing the last map on Hard (甲) mode will reward a First Class Medal. The First Class Medal can still be obtained even if earlier maps were done on easier difficulties, as long as the last map is cleared on Hard.Clearing the map before on Easy (丙) mode, will lock out Hard (甲) mode for the last map, so pay attention if you wish to collect the First Class Medal.

Note that the original Japanese words for the three difficulty tiers (which literally mean A/B/C) does not immediately convey the difficulty of the mode. Instead, their difficulty were indicated by the number of sakura petals below the ranks, where more petals indicate a higher challenge. They're translated as such for the purpose of simplicity.

Requirements

 * Easy difficulty is always unlocked
 * Medium is unlocked at HQ level 35
 * Hard is unlocked at HQ level 80

Constraints

 * Players may not change the difficulty after clearing the map (emptying the boss gauge).
 * Players may change the difficulty anytime before clearing the map, but the boss gauge will be fully restored upon doing so.
 * Players may not select Hard difficulty if the previous map was cleared on Easy . It's possible to jump to and from other difficulties though.

Easy Mode Ship Lock
Starting from the Spring 2015 Event, players on Easy mode would not have shiplock restrictions, allowing the the players to send shiplocked girls to maps not normally allowed. For example : If you used Ooi in E-4 Hard mode, you can use her in E-5 Easy mode, since easy mode allows using shiplocked girls. But if you used Mogami in E-2 on Easy, you cannot use her in E-4 Medium or Hard modes. back to Table of Contents

LoS Check
Starting from the Spring 2014 Event event, LoS -based checks were implemented. A fleet's total or equipment LoS affects movement throughout the map for certain nodes and the boss node. This mechanic has then been implemented onto normal and extra operation maps released since. LoS checks are dependent on Admiral HQ level. The exact calculation formula can be referred to here. back to Table of Contents

Manual Node Selection
Introduced in Spring 2015 Event, certain nodes allow you click on the map to specify which route you want to take. You may only choose the nodes that are connected directly to the manual nodes.

back to Table of Contents

Boss Debilitation Mechanism
First introduced in Summer 2015 Event (see here).

The mechanism requires players to fulfill specific requirements on the map in order to be able to increase damage dealt to the boss. This mechanic resets at 0000 JST daily. Without using this mechanic, the boss will ultimately be harder to defeat. The mechanism also appears to persist even when difficulty settings are changed.

In Summer 2015 Event, the only map that used this mechanic was E-7. Initial speculation and testing indicated that the debilitation nodes were X and Y. However, a source that appeared after the event indicated that node C was also another debilitation node. In this event, this mechanic increased all ships' critical damage multipliers and possibly critical hit rates at the boss node. Other than boss node (node Z) the debilitation nodes are shown.

The Fall 2015 Event version of the mechanic involved the Submarine Princess and the Destroyer Water Demon, requiring the player to defeat certain enemies on the map enable it. Unlike the previous event which lacked any visible indicators, enemy bosses now have a separate CG and lines to indicate their weakened version.


 * The Fall 2015 Event E-5 boss, Destroyer Water Demon could be debilitated by sinking at least 30 PT Imp Packs during the TP-Bar Stage or 15 PT Imp Pack during Boss HP Bar Stage. While the debilitation was in effect, the Destroyer Water Demon would lose her helmet.

The boss debilitation mechanism effect lasts until 05:00 hrs JST on Fall 2015 Event, except for the last day of the event. back to Table of Contents

Transport Load-Off gauge
First introduced in Fall 2015 Event, where players are able to equip Drum Canister and/or Daihatsu Landing Craft to ships in order to deplete a gauge known as Transport Load-Off gauge. Depending on the map, players may be allowed to set up a new type of Combined Fleet known as Transport Escort Fleet (輸送護衛部隊 yusou goei butai).

The players are required to visit nodes indicated with a flag. From there, the game will note how many Drum Canister/Daihatsu Landing Craft the player's fleet has carried. The player is then required to get an A rank or higher at the boss node in order to deplete points off the Transport Load-Off gauge. (揚陸成功した輸送物資量? youriku seikoushita yusoumono shi ryou)

In the case of Fall 2015 Event, E-2 utilized the Transport Load-Off gauge, but was designed for a single fleet. Fall 2015 Event's E-3 used Combined Fleet, with the Transport Escort Fleet (輸送護衛部隊 yusou goei butai) option enabled. Fall 2015 Event's E-5 had a dual gauge system, where after depleting the TP gauge, the HP gauge would be revealed and would have to be depleted again to truly clear the map.

'''The same logic applies to the mechanics of difficulty selection and specifically the Hit Point (HP) gauge. If you reset your difficulty selection at any time in a specific map for whatever reason, you will reset both the HP and TP gauge of that map, even if the TP gauge has already been cleared. You will have to redo the TP gauge once again.'''

Here is some of the known information collect about the Transport Load-Off gauge mechanism: TP Calculation, according to data obtained from nga178 forum (Chinese), wikiwiki calculation, and a TP Calculator based on the NGA method (Chinese) back to Table of Contents
 * TP calculation is not affected by Map.
 * According to the Japanese wikiwiki source, TP point calculation has been changed since Fall 2015.
 * For S Rank victory, after TP calculation, the total is rounded down.
 * For A Rank victory, after TP calculation, the total is rounded down, multiplied by 0.7, and then rounded down again.
 * The TP Gauge won't change if the battle results in a B-Rank or lower.
 * Each Combat Ration give approximately 1 extra TP. No data for Canned Mackerel or Underway Replenishment yet.
 * How Combat Ration consumption affects the value is still unknown.
 * Ships that reach the flag node with taiha (大破) status or being retreated (撤退 via Fleet Command Facility) are not calculated in the node, as well as their equipment loaded.
 * Icon popups will appear when reaching the flag node, displaying the number of Drum Canister/Daihatsu Landing Craft that were brought.
 * TP is rounded down after being summed.
 * Other unlisted ship types, like CLT? / CA?  have not been tested.
 * Daihatsu Landing Craft related calculations are not accurate and require further data.

HP Bar Scaling
Starting from the Summer 2015 Event, the required amount of boss kills required to clear a map has varied depending on an Admiral's HQ Level. The higher the HQ Level is, the more kills needed to complete a map.

Here is an example from Winter 2016 event:

For example, to complete E-1 in Easy difficulty, a HQ105 Admiral would require 5 kills, while a HQ30 Admiral would need only 3.

However, it is still unknown whether there are more threshold levels aside from the ones that already exist in the table above. back to Table of Contents

Multiple Branching Map
Starting from Winter 2016 Event, some maps with multiple branching options came into existence. These maps may have multiple starting or/and ending nodes. Going from one route depends on the ships which are used to sortie on the map.

As shown in the image, there were multiple start and end nodes in 2016 Winter event E-3 map. The first part was to deplete TP gauge by using a Transport Escort Fleet which starts with node A and ends at node S. After which, players had the option of using either a Surface Task Force (starts with node J) or Carrier Task Force (starts with node E or F) to make their way to the final boss (node T).

In this map, if players attempt to change the difficulty, both the HP and TP bars will be reset, forcing players to clear both gauges again.

back to Table of Contents

Air Raid Battle (空襲戦)
First introduced in Winter 2016 Event. At this point in time it is not confirmed whether or not will this mechanism be here to stay for good.

Unlike Aerial battle nodes as seen in Summer 2014 Event where it was possible to attack Abyssal ships through Dive/Torpedo Bomber planes, Air Raid Battle nodes are strictly defensive air battles against an onslaught of Abyssal aircraft before they attempt to damage your ships.

There are a few key differences with an Air Raid Battle versus a regular aerial battle:
 * The nodes are indicated by a single red arrow curving towards a red circle.
 * Given the fact that diamond formation offers the highest anti-air modifier, it is advised to use it in these nodes.
 * Receiving no damage from an Air Raid Battle yields S ranking. However, receiving one damage results in A rank. Detailed rules:
 * Perfect S: Take zero damage from the airstrike. Annihilation of enemy bombers isn't necessary.
 * A: Take less than 10% damage
 * B: Take 10%-20% damage
 * C: Take 20%-50% damage
 * These nodes consume 8% fuel and 4% ammo.
 * If a ship's total fuel/ammo is not divisible by 4%/8%, the cost would be rounded up.
 * Abyssal aircraft from Installations such as Variant V/VI/VII of Airfield Princess will attenmpt to bomb your fleet. (Note that there will be no "plane launching" animation) Your fleet will launch any aircraft able of participating in the Aerial Combat phase to intercept them. No bombers will attack, nor will the enemy have a formation.
 * Airfield Princesses that appear on these nodes tend to use the following aircraft:
 * Abyssal Liberation Land-based Dive Bomber
 * Abyssal Liberation Land-based Dive Bomber Ace
 * Note that these are not the only aircraft that appear in air raid nodes, nor do they exclusively appear in air raid nodes.

back to Table of Contents
 * You cannot choose to pursue the enemy for night battle, as you are not fighting with an enemy fleet, but instead defending yourself from an enemy air raid.