Randomness - Revision history

Slade at 13:15, 21 January 2024

2024-01-21T13:15:09Z

← Older revision		Revision as of 13:15, 21 January 2024
Line 69:		Line 69:
	;		;
	}		}

			=== example implementation in python3 ===
			#!/usr/bin/env python3
			state = [0] * 16

			def rng():
			carry = 0
			for i in range(15,0,-1):
			carry, state[i-1] = divmod(carry + state[i-1] + state[i], 256)

			for i in range(15,-1,-1):
			state[i] = (state[i] + 1) % 256
			if state[i] != 0:
			break
			return state[0]

			for _ in range(20):
			print(hex(rng()))

Crediar: /* Randomness Advancements */

2022-01-17T18:56:53Z

Randomness Advancements

← Older revision		Revision as of 18:56, 17 January 2022
Line 5:		Line 5:
	* Ark gets hit		* Ark gets hit
	* Enemy gets hit		* Enemy gets hit
	* Enemy logic calls ~~rand()~~		* Enemy logic calls the random function
	* NPC randomly walks around		* NPC randomly walks around
	* Sprite animations		* Sprite animations

Crediar: /* Manipulations */

2021-04-10T16:21:14Z

Manipulations

← Older revision		Revision as of 16:21, 10 April 2021
Line 13:		Line 13:
	*Ghost fight		*Ghost fight
	*Dragoon Castle guard pattern		*Dragoon Castle guard pattern
	*Dark Gaia		*Dark Gaia
			*Quintet Quiz

	== Code ==		== Code ==

Crediar: Started page

2021-04-10T16:16:59Z

Started page

New page

The randomness is at 0x7E0408 and is 16 bytes. It is set to all zero on reset of the game.

== Randomness Advancements ==
* Ark idle animation
* Ark gets hit
* Enemy gets hit
* Enemy logic calls rand()
* NPC randomly walks around
* Sprite animations

== Manipulations ==
Since on reset the randomness has a known starting point and a predicable continuation of the values, it is possible in certain cases to manipulate it.
*Ghost fight
*Dragoon Castle guard pattern
*Dark Gaia

== Code ==
Note: This is simply translated from the assembler code

typedef unsigned char u8;
typedef unsigned char u16;

u8 seed[16];

void random( u8 *seed )
{
u8 x = 0xF;
u8 a = 0;
u8 b = 0;
u8 c = 0;

loc_C68242:
a = seed[x];

u8 r = 0;

if( a + c + seed[x-1] > 0xFF )
r = 1;
else
r = 0;

a += c + seed[x-1];

c = r;

seed[x-1] = a;
x = x - 1;
if( x > 0 )
goto loc_C68242;

x = 0x10;

loc_C68251:
if( seed[x-1] + 1 > 0xFF )
r = 1;
else
r = 0;

seed[x-1] += 1;
if(r==0)
goto loc_C68259;

x = x - 1;
if( x > 0 )
goto loc_C68251;

loc_C68259:
;
}