;Enhanced Low Gravity/Floaty Luigi Physics, by Blind Devil (revision 2018-10-16)
;This file applies a change to the player jumping physics, and alters its pose
;accordingly if set to do so. The configuration can be applied to all player
;characters, to a specific character or can be RAM flag dependent. You also
;have the option to use flutter animation or not.

;You should place this in the library folder, and call it from your level or game
;mode 14 (main) code like this:

;LDA #%xxxxxxxx		;these are the option bits
;JSL Floaty_runcode	;format: filename_labelname

;Option bit usage:
;----RFLM
;M = enable floaty physics for player 1.
;L = enable floaty physics for player 2.
;F = use flutter animation.
;R = make floaty physics flag-dependent (overrides bits 0 and 1 options).
;---- = unused.
;Values for each bit can be either 0 or 1. If M, L, or R are zero, this code
;is useless.
;Example: If you want to enable floaty physics for player 2 only, and use
;fluttering animation, you use this before the JSL:
;LDA #%00000110

;Configurable define:
;FREE RAM FLAG
;What address to use as a flag to enable/disable floaty physics.
;If the bit option is not used, this RAM is untouched.
!FloatyFlag = $0DDD|!addr

;Code starts below.

runcode:
STA $00			;store value in A to scratch RAM.

AND #$08		;preserve bit 3
BEQ .UseNoFlag		;if bit is not set, don't use flag.

LDA !FloatyFlag		;load RAM flag
BNE .ProcessFloaty	;if not equal zero, process physics.

.NoProc
RTL			;just return and process nothing.

.UseNoFlag
LDA $00			;load user-defined bits from scratch RAM
AND #$03		;preserve bits 0 and 1
CMP #$03		;compare to value
BEQ .ProcessFloaty	;if equal, process physics for both players.
CMP #$02		;compare again
BNE +			;if not equal, skip ahead.

LDA $0DB3|!addr		;load character in play
BNE .ProcessFloaty	;if not player 1, process physics.
RTL			;else, just return and process nothing.

+
CMP #$01		;compare again
BNE .NoProc		;if not equal, return.

LDA $0DB3|!addr		;load character in play
BNE .NoProc		;if not player 1, don't process physics.

.ProcessFloaty
LDA $75			;load player is in water flag
ORA $1407|!addr		;OR with cape flying phase
ORA $1B89|!addr		;OR with message box timer/size
ORA $1471|!addr		;OR with what kind of platform/sprite player is standing on
ORA $18BD|!addr		;OR with stun player timer
BNE .NoProc		;if result is not zero, don't use low gravity.

LDA $72			;load player is in the air flag
BEQ .NoFlutter		;if not in the air, don't change pose.

LDA $00			;load user-defined bits from scratch RAM
AND #$04		;preserve bit 2
BEQ .NoFlutter		;if bit is not set, don't change pose.

LDA $73			;load player ducking flag
ORA $74			;OR with player climbing flag
ORA $71			;OR with current player animation settings
ORA $140D|!addr		;OR with spin jump flag
ORA $149C|!addr		;OR with shooting fireball timer
ORA $14A6|!addr		;OR with cape spin timer
ORA $187A|!addr		;OR with riding Yoshi flag
BNE .NoFlutter		;if result is not zero, don't change pose.

LDA $148F|!addr		;load player is carrying an item flag
BNE .carrying		;if yes, branch to use carrying flutter pose.

LDA $14			;load effective frame counter
LSR			;divide by 2
AND #$01		;check if bit is set
BNE .flutter2		;if set, branch.

LDA #$00		;load pose value
BRA .storepose		;branch to store pose.

.flutter2
LDA #$02		;load pose value
BRA .storepose		;branch to store pose.

.carrying
LDA $14			;load effective frame counter
LSR			;divide by 2
AND #$01		;check if bit is set
BNE .flutter4		;if set, branch.

LDA #$07		;load pose value
BRA .storepose		;branch to store pose.

.flutter4
LDA #$09		;load pose value

.storepose
STA $13E0|!addr		;store A value to display pose.

.NoFlutter
LDA $13D4|!addr		;load game paused flag
ORA $9D			;OR with sprites/animation flag locked
BNE ++			;if both aren't zero, return.

LDA $77			;load player blocked status
AND #$1C		;preserve bits 2, 3 and 4 (within a block, touching ceiling and touching ground)
BNE ++			;if any bits are set, return.

LDA $7D			;load player's Y speed
CMP #$80		;compare to value (highest upwards)
BEQ ++			;if equal, don't decrement - prevent overflow

DEC $7D			;decrement player's Y speed by one every frame

++
RTL			;return.