;===========================================================
; Ice Rod freezes water
; Written by Conn
; 
;===========================================================

namespace IceRod
{
  Main: 
  {
    lorom

    org $088a5d ; jsl to main code
    jsl $0efba0


    org $0efba0 ; main code
    STA $03E4,x ; load native value
    TAY 
    LDA $008C ; check if you're on overworld 
    BNE $01 
    RTL 
    LDA $03A3 ; disable other flying object icing water (boomerang, sword beam) 
    CMP #$06 
    BEQ $01 
    RTL 
    CPX #$04 ; check if ice shot #1 only is used (disable 2nd shot to ice) 
    BEQ $01 
    RTL 
    LDA $03E8 ; check if ice shot is on water tiles 
    CMP #$08 
    BEQ $08 
    LDA $03E8 ; check if ice shot is on native unused, edited blocks 
    CMP #$03 
    BEQ $01 
    RTL
    LDA $0303 ; double check if really ice shot is used
    CMP #$06 
    BEQ $01 
    RTL 
    LDA $0304 
    CMP #$06
    BEQ $01 
    RTL 
    TXA 
    STA $7ED004 ; store native x value into ram to regain after code
    LDA $4212 ; wait for vblank to enable dma transfer
    AND #$80 
    BEQ $F9 
    REP #$30 
    LDA $2116 
    STA $7ED005 ; store native value to regain later 
    LDA $00 ; calculation procedure to get correct x,y coordinates for new tile
    SEC 
    SBC $0708 
    AND $070A 
    ASL A 
    ASL A 
    ASL A 
    STA $06 
    LDA $02 
    SEC 
    SBC $070C
    AND $070E 
    ORA $06 
    TAX 
    LDA #$00B7 
    STA $7E2000,x ; store new 16x16 ice tile into ram (property of tile!)
    CLC 
    STZ $02 ; calculation procedure to get 8x8 vram map address (look of tile)
    TXA 
    AND #$003F 
    CMP #$0020 
    BCC $05 
    LDA #$0400 
    STA $02 
    TXA 
    AND #$0FFF 
    CMP #$0800 
    BCC $07 
    LDA $02 
    ADC #$07FF 
    STA $02 
    TXA 
    AND #$001F 
    ADC $02 
    STA $02 
    TXA 
    AND #$0780 
    LSR A 
    ADC $02 
    STA $2116 ; store vram address for upper tile part (8x16) to $2116
    STA $7ED007
    LDA #$1D83 ; load new ice tiles
    STA $7ED000
    STA $7ED002
    JSR $FD00 ; jsr to dma vram transfer for upper ice tile part
    REP #$30 
    LDA $7ED007 ; regain vram address
    ADC #$0020 ; add 20 for lower part (8x16) and store to $2116
    STA $2116 
    JSR $FD00 ; jsr to dma vram transfer for lower ice tile part
    LDA $7ED005 ; regain native register value
    STA $2116
    SEP #$30 
    LDA $7ED004 ; regain native x-value
    TAX 
    RTL 


    org $0efd00 ; vram dma transfer
    LDA #$007E ; load origin of bytes to transfer (7E/d000)
    STA $4304 
    LDA #$D000 
    STA $4302 
    SEP #$30 
    LDA #$18 ; bus
    STA $4301 
    LDA #$04 ; transfer 4 bytes 
    STA $4305 
    LDA #$01 
    STA $4300 
    STA $420B ; make dma transfer
    RTS 


    ; bug fix to not swim through tiles but jump onto them

    org $07dc9e
    jsl $0efc80
    nop

    org $0efc80
    LDA $0A 
    TSB $0343 
    TSB $0348 
    RTL 

    ; bug fix to stop gliding on shallow water when leaving ice tile 

    org $07dd1b 
    jsl $0efc90
    nop

    org $0efc90
    LDA $0A 
    TSB $0359 
    LDA $0350 
    CMP #$0100 
    BNE $03 
    STZ $034A 
    RTL 


    org $0e95dc ; get a 0e written here (first byte) to enable gliding on new tiles
    ASL $5757

    org $0f85b8 ; get new tile values (83 1d) written 4 times here
    STA $1D,s 
    STA $1D,s 
    STA $1D,s 
    STA $1D,s
  } 
}  ; namespace IceRod