546 - bombShield(int a, int script)

Sets the bomb invulnerability flag (a=0 false, a=1 true), the caller's ANM script will change to script when a bomb is active.

611 - etEx(int etId, int async, int type, float a, float b)

Adds bullet transformation to bullet manager etId, Transformation of flag type determines the specific behaviour of the bullet. Documentation can be found here.

BulletEffectType-67108864 - etExDelay(string et, string isAsync, string time)

Hide the bullet for time frames. During this time, it will not move, will be invisible and won't have a hitbox. If used as a first transformation, can be used to delay when the bullet actually appears.

6 - isDelayedSpawn

While this flag is set, the bullet will be invisible and not have a hitbox. This flag is cleared once the delay timer ends.

4 - short_timer

Integer value between -1 and 15 inclusive (by default -1). If non-negative, shooters using short_timer shoot their bullets and timer increments by 1 per frame until 15 is reached. Once 15, timer reset to -1 or 0 depending on Z key state.

5 - long_timer

Integer value between -1 and 120 inclusive (by default -1). If non-negative, shooters using long_timer shoot their bullets and timer increments by 1 per frame until 120 is reached. Once 120, timer reset to -1 or 0 depending on Z key state.

503 - flagClear(int n)

Clears flag(s) according to n. Refer to the flag table here for exact values.

91 - floatTime(int slot, float var, int time, int mode, float start, float final)

In time frames using mode mode, variable var changes from start to final. slot is used to set the slot to be used by this ins, every enemy has 8 slots.

-9980 - F1

Local float variable, inherited by spawned enemies.

-9984 - I1

Local integer variable, inherited by spawned enemies.

-9989 - ANGLE_PLAYER

Angle from the enemy to the player.

-9962 - BOSS_Y

Final Y position of the boss.

-9990 - PLAYER_Y

Player's Y position.

-9963 - BOSS_X

Final X position of the boss.

-9991 - PLAYER_X

Player's X position.

81 - circlePos(float varX, float varY, float angle, float radius)

Performs following operation: varX = cos(angle) * radius and varY = cos(angle) * radius

-9981 - F0

Local float variable, inherited by spawned enemies.

300 - enmCreate(string sub, float x, float y, int hp, int score, int item)

Creates an enemy using subroutine sub at coordinates (x, y) (relative to position of the parent), health of created enemy is hp, score bonus is score and item drop is item.

601 - etOn(int etId)

Shoots bullet(s) using properties from bullet manager etId.

23 - wait(int time)

Stops sub execution for time frames.

1 - delete()

Returns to the top of current call stack.

2 - GAME_SPEED

The value controls by how much faster the game speed is run. This variable is often set to a number between 0 and 1. This value is often changed when a (final) boss dies or when a photo is taken. Its default value is 1.

-9985 - I0

Local integer variable, inherited by spawned enemies.

-9983 - I2

Local integer variable, inherited by spawned enemies.

-9982 - I3

Local integer variable, inherited by spawned enemies.

-9954 - ENEMY_HP

Enemy's current HP.

3 - goheiExists

A flag that determines if a gohei exists on-screen or not. Flag is set to true by active gohei. Flag is set to false if gohei goes off-screen or is despawning.

-9926 - GI0

Global integer value. Value is initialised to 0 on stage load but not on stage reset.

-9925 - GI1

Global integer value. Value is initialised to 0 on stage load but not on stage reset.

-9924 - GI2

Global integer value. Value is initialised to 0 on stage load but not on stage reset.

-9923 - GI3

Global integer value. Value is initialised to 0 on stage load but not on stage reset.

17 - distortion(int a)

Triggers distortion effects on the edge of the screen. The meaning of the argument is not entirely clear. SA uses a value of 1 to create distortion at the bottom of the screen, while UFO uses this same value to create distortion at the top.

539 - spell3(int id, int timeRate, int unused, string name)

Declares a spell-card with id id and name unused. The ID passed to the spell-creating function is id + difficulty - 2 (with easy=0, normal=1, ..., overdrive=5). timeRate determines how much time the spell circle takes to shrink (in frames), as well as how fast the spell bonus decreases.

514 - setInterrupt(int slot, int hp, int duration, string subroutine)

Sets an interrupt on slot slot. Once caller's HP reaches hp or duration frames have passed since this instruction was called, the caller will terminate all subroutines it's currently running and execute subroutine subroutine.

270 - enmCreate270(string sub, float x, float y, int hp, int score, int item)

Creates an enemy using subroutine sub at coordinates (x, y) (relative to position of the stage background camera), health of created enemy is hp, score bonus is score and item drop is item.

115 - timer_callback_threshold(int time)

Calls the callback function timer_callback_sub after time frames have passed.

10022 - SELF_TIME

Integer value that increases by 1 every in-game frame. This value is used by bosses and by functions such as timer_callback_threshold.

7 - has_been_inbounds

This flag is set when the enemy has been within bounds. The default value is false.

8 - is_in_bounds

This flag is set when the enemy is currently within bounds. This flag is false if it is out of bounds.

Persisting Bat State

Specifications

  • Versions: 1.00 - 1.01 - 1.02 - 1.02a - 1.02b - 1.02c - 1.02d - 1.02e - 1.02f - 1.02h
  • Difficulty: Easy - Normal - Hard - Lunatic - Extra
  • Mode: Main game - Practice mode
  • Shottype: ReimuA - ReimuB - MarisaA - MarisaB

What happens

Flandre and Remilia can remain in their bat form for a long time. This effect lasts for 50 seconds before the stage progresses.

Image of Remilia and Flandre being bats.
Figure 1: Remilia and Flandre staying in their bat form after their final spell-card.

How it happens

To replicate this, you must have a bomb active before timing down the final spell-card of Remilia or Flandre. By bombing, Remilia or Flandre will turn into a bat until the bomb is no longer active. While they are in their bat form, they become immune to any damage source.

Why it happens

There are two issues present here. Firstly, the boss remains in her bat state. Secondly, the stage doesn't continue until 50 seconds later. Both are explained in the following sections.

Bat state

During any of Flandre's spell-cards and during Remilia's final spell-card, a special instruction update_bat_form is run every frame that manages their bat state. Its pseucode representation is as follows:

bat_timer = 0
boss_is_tangible = true

void update_bat_form():
    if enemy_health <= 0:
        return

    if player_bomb_is_active:
        bat_timer = 60
        set_state(BAT_FORM)
        boss_is_tangible = false
        return

    if bat_timer <= 0:
        return

    bat_timer -= 1

    if bat_timer == 0:
        set_state(NORMAL_FORM)
        boss_is_tangible = true
  • bat_timer determines how long Remilia or Flandre stays for in their bat form in frames.
  • boss_is_tangible determines whether or not the enemy can take damage or not.

If no bomb is used at all, then bat_timer remains at 0 so this function does not execute anything meaningful. However, if there is an active bomb, then the code in the block player_bomb_is_active is run, turning Flandre/Remilia into a bat. Right after the bomb has expired, Flandre/Remilia remain as bats. Once 60 frames have passed without player_bomb_is_active being active, Flandre/Remilia return to their normal state.

When timing out any of Flandre's spell-cards except her final spell-card, the update_bat_form stops running and a direct call to set_state(NORMAL_FORM) is made. However, when timing out Flandre's or Remilia's final spell-card the update_bat_form again stops running but no call to set_state(NORMAL_FORM) is made. This explains why Flandre or Remilia stay in their bat form after their final spell-cards.

Timing down a final spell-card

When timing out a final spell-card, you may have noticed that the boss explodes twice. This is because the boss actually invokes the same code twice due to the way callbacks are handled. A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action. In particular, we are interested in the following two callbacks:

  1. The timer_callback_sub(func), which is triggered when the timer reaches 00s.
  2. The death_callback_sub(func), which is triggered when the boss reaches an HP threshold of 0 HP.

If a final spell-card is timed down, first the timer_callback_sub invokes sub_boss_death, which spawns some particle effect, plays some sounds and sets the boss HP to 0. However, because sub_boss_death sets the boss HP to 0, it means that death_callback_sub invokes sub_boss_death. This means that it is repeated twice.

However, when the boss is in her bat form, the death_callback_sub never gets run. One of the requirements for death_callback_sub to be run is for boss_is_tangible to be true, but since the boss is in her bat form, boss_is_tangible is false. Since death_callback_sub is never run, the code continues to run the final instructions. For both Remilia and Flandre, the code explicitly states for both to wait for 3000 frames (50 seconds) until the enemy is deleted by the code.

Replays

  • Replay ex-bug by "kana0603". Extra, MarisaB, 1.02h. 「June 1, 2026」. Download link
  • Replay s6-bug-L by "kana0603". Lunatic, ReimuB, 1.02h. 「June 1, 2026」. Download link
  • Replay s6-bug-N by "kana0603". Normal, ReimuB, 1.02h. 「June 1, 2026」. Download link

Videos

This section has no content yet. Would you like to add to this section? Contact me if you are interested!