Random Number Generation

Turn Order

During the first turn of each Battle Windows enemy, there is a 25% chance for Battle Windows to attack first. This is a notorious point of chance in the run where time can be lost if Battle Windows gets the first attack.

When Battle Windows attacks first, time loss can vary depending on the attack that is done. The worst possible luck is having an enemy shield on their first turn, which requires a whole additional turn to defeat it.

In specific circumstances, it is actually beneficial to have Battle Windows to attack first, but this is typically only done in TAS. An example of this is using Suplex while fighting Red Dragon. By having Red Dragon attack first, Kirby can grab its scratch attack and defeat it in one turn.

Procedure

Calculating the outcome for first turn attack uses one RNG number.

Slime and Magician:

64 < RNG < 127: Battle Windows attacks first
Else: Kirby attacks first

Puppet and Dark Knight:

128 < RNG < 191: Battle Windows attacks first
Else: Kirby attacks first

Red Dragon:

192 < RNG < 255: Battle Windows attacks first
Else: Kirby attacks first

Attacks

Attack choice advances one RNG number.

Every Battle Windows enemy has two attack pools to choose from, which is based on if RAM value 179C is an even or odd number. This number changes between 0 and 1 after each time Battle Windows attacks, first starting on 0.

This RAM value will not change on Battle Window's first attack (whether that be first turn or not).
This RAM value seems to change, but freezing this value does not seem to alter the attack pool. More research is required.

Slime

The only move that deals damage is Star Shot. The rest of Slime's moves do nothing.
Slime only attacks every two turns.

RNG

Attack Pool 1

Attack Pool 2

0 - 25

Stars

Call for help

26 - 51

Sleep

52 - 76

Stars

Call for help

77 - 102

Tries to escape

103 - 127

Stars

Sleep

128 - 153

Call for help

154 - 179

Stars

Call for help

180 - 204

Stars

Sleep

205 - 230

Surprised

231 - 255

Stars

Sleep

Attack Messages

Ability Appearance

When it is Kirby's turn to attack, abilities have a chance of appearing on each side of the screen. Several random numbers are used during this process. This calculation is different from power calculation in The Arena rest area.

Procedure

Flowchart depicting how Battle Windows uses RNG.

If an ability does not appear, RNG advances by 1, while if an ability does appear, RNG advances by 3. RNG can advance at least 2 times or at most 6 times when calculating powers (unless under a specific circumstance, see notes below).

1.) Determine if a power will appear on the right side:
- 64 < RNG < 127: Power appears
- Else: Does not appear (Skip steps 2 and 3)

2.) Determine which pool to choose from:
- 0 < RNG < 63: Pool 1 (Sprite number 90)
- 64 < RNG < 127: Pool 2 (Sprite number 91)
- 128 < RNG < 191: Pool 1 (Sprite number 90)
- 192 < RNG < 255: Pool 2 (Sprite number 91)

3.) Choose a power from the pool chosen:

RNG	Ability Pool 1	Ability Pool 2
0 - 21	Fighter	Stone
22 - 42	Plasma	Cutter
43 - 63	Hammer	Wheel
64 - 85	Beam	Jet
86 - 106	Bomb	Ice
107 - 127	Sword	Parasol
128 - 148	Hammer	Fire
149 - 170	Bomb	Suplex
171 - 191	Plasma	Ninja
192 - 213	Sword	Yo-yo
214 - 233	Beam	Mirror
234 - 255	Fighter	Wing

4.) Determine if a power will appear on the left side:
- 128 < RNG < 191: Power appears
- Else: Does not appear (Skip steps 5 and 6)

5.) Same as step 2
6.) Same as step 3

Notes:

If no abilities appear for 3 consecutive turns, abilities will appear from both sides on the next turn (steps 1 and 4 are skipped). This is tracked in the game's memory.
In the rare circumstance that abilities appear on both sides, and both sides contain the same ability, step 4 will be repeated again after step 6. This will continue to repeat until either both abilities are different, or the left side ability does not appear.

RAM Values

All currently known RAM values associated with Battle Windows.

Domain	Address	Description	Procedure	Function
CARTRAM	1790	Idle Timer	Starts at 104, then loops to 255 for a total of 360 frames. Counts down once every frame.	Kirby's turn is up when this value reaches 0.
CARTRAM	1791	Attack state?	Changes based on Battle Windows attack. Needs more research.
CARTRAM	179C	Even or Odd Turn	Value switches between 0 and 1 after each turn.	Alters which attacks are used in each RNG range. However, freezing this value doesn't seem to do anything. More research required.
CARTRAM	1838	Timer (after attack)	Value stays at 255 until Kirby attacks Battle Windows at least once. After first Battle Windows hit, counts down from 90 once every frame.	Kirby's turn is up when this value reaches 0.
CARTRAM	1888	Timer for text scroll	Needs more research
More to come...