Custom scrolling

init:
    STZ $1411
RTL

main:
    STZ $04 : STZ $05 : STZ $06
    LDX #$0C
    -
        DEX
        BMI +
        LDA $9E,X
        CMP #$63
        BNE -
        LDA $14C8,X
        CMP #$08
        BMI -
        LDA $04
        CLC : ADC $E4,X
        STA $04
        LDA $05
        ADC $14E0,X
        STA $05
        INC $06
        LDA $06 : CMP #$02
    BNE -
        LSR $05
        ROR $04
    -
        LDA $04
        SEC : SBC #$80
        STA $1462
        LDA $05
        SBC #$00
        BMI ++
            STA $1463
        RTL
        ++
        STZ $1462 : STZ $1463
    RTL
    +
    LDA $06
    BNE -
    LDA #$01 : STA $1411
RTL