// Calculate Pixel Error - Steep slopes
    // Y = DeltaY
    // X = DeltaX

    lda FractionTableLo,y
    sta !SMC1++1
    sta !SMC3++1
    eor #$ff
    sta !SMC2++1
    sta !SMC4++1
    lda FractionTableHi,y
    sta !SMC5++1
    eor #$ff
    sta !SMC6++1
!SMC1:
    lda Square1Lo,x
    sec
!SMC2:
    sbc Square2Lo,x
!SMC3:
    lda Square1Hi,x
!SMC4:
    sbc Square2Hi,x
    clc
!SMC5:
    adc Square1Lo,x
    sec
!SMC6:
    sbc Square2Lo,x
    // A = Pixel Error

    .align $100
    .pc = * "Math Tables"
FractionTableHi:
    .fill 256, >round(65536 / i) + 0.5
FractionTableLo:
    .fill 256, <round(65536 / i) + 0.5
Square1Lo:
    .fill 512, [i*i/4] & $ff
Square1Hi:
    .fill 512, [i*i/4] >> 8
Square2Lo:
    .fill 512, [[[i-255]*[i-255]]/4] & $ff
Square2Hi:
    .fill 512, [[[i-255]*[i-255]]/4] >> 8