smooth hp bar scrolling

UpdateHPBar_AnimateHPBar: ; fab1 (3:7ab1)
    push hl
.barAnimationLoop
    push af
    push de
    ld d, $6
    call DrawHPBar
    ld a, [wHPBarType]
    dec a ; battle hp scroll, player
    ld a, TRANSFERMIDDLE
    jr z, .delayframe
    ld a, [wHPBarType]
    and a ; battle hp scroll, enemy
    ld a, TRANSFERTOP
    jr z, .delayframe
; status screen
    ld a, [wcf06] ; wUsedItemOnWhichPokemon
    cp $3
    ld a, TRANSFERTOP
    jr c, .delayframe
    ld a, TRANSFERMIDDLE
.delayframe
    ld [H_AUTOBGTRANSFERPORTION], a
    call DelayFrame
    pop de
    ld a, [wHPBarDelta] ; +1 or -1
    add e
    cp $31
    ; ...